Changes

Software is copyrightable, but the source code can be made available to users however the author chooses. A copyright license is a legal document that tells people how the software can be used and what limitations come with using it.-->

The more successful emulation projects ==Intellectual property law==Explaining all of this requires an understanding of the fundamentals. Intellectual property is a mouthful, but it refers to the ownership of things by nature of originality. There are often open source (though you definitely will find exceptions)three big fields of intellectual property law; copyright, patents, and trademarks, and are all used for different things.

==Public domain==There ;Patents:System design and inventions. An author designs a system (an invention), and then describes it in detail for others to implement. This is no copyright usually something you register at an agency (i.e. No Rights Reservedsuch as the United States Patent and Trademark Office if you live in the United States). Works enter the public domain when they:;Trademarks:# were released before the current copyright expiry dateNames and brands. This is why old paintings, playsAn author comes up with a name that identifies their products, and books are so commonly quoted and used ensures that nobody else in modern works, because they'd have to negotiate the rights with the author otherwisesame industry can use it. Most software This is not released this way because it is still covered by usually something you register at an agency (such as the United States Patent and Trademark Office if you live in the current American copyright termUnited States).;Copyright:# are dedicated through a license like Creative Commons Zero or the Unlicense. This is the only option for modern works to be released into the public domain because, per the Berne Convention, copyright is seen as opt-out, not opt-in. If An author creates a work (sometimes called a public domain dedication work of art but that's misleading because it assumes everything that can't be made (probably because the jurisdiction doesn't recognize the public domaincopyrighted is art), and then licenses this work to others for reproduction. Is designed to be granted as soon as the license grants users work is created, unlike the equivalent freedomsother two.

==Open-source=Legal entities===The program is released under owner of intellectual property doesn't have to be a copyright license that permits four freedoms: that it can be run at person; if an employee does any timekind of IP-related work for a company, studied and modified for then the user's own purposes, distributed to anyone, and improved for everyone else. This bypasses most company may retain control of it depending on the issues encountered terms they've set up with public domain workssaid employee through contracts. For anything else copyrightableThat contract may also contain clauses preventing the employee from speaking publicly about the work that goes on inside, the term "open content" since trade secrets are considered valuable. This is often appliescalled a non-disclosure agreement (NDA).

Common open-source licenses:===Public domain===*'''GNU GPL''' - Based on the original design of copyright, we know that the time that a work stays protected is supposed to be finite; that is, it should expire. This is a copyleft license, everybody has because the freedom to do whatever they like with protection originally lasted fourteen years from the software (even selling date of a work's creation when it), was originally conceived in the only caveat is: if you make changescommonwealth, you have as a way to publish the modified source code upon requestincentivize further creation of works.*But because long-running companies want to continue profiting off of old work, they set precedents in modern law that extend this time to as long as '''MIT/BSD/Apache 2.0one hundred years''' - These three are basically the same and similar to ''Public Domain''. In many western countries, you companies have complete freedom and can do whatever you like a love-hate relationship with the software. The difference between this and ''GPL'' is public domain, wilfully using works that these are not copyleft: you can fork a project and turn in it closed-source, you don't have to publish the source code changeswhile preventing their transformations from being misused.

It's worth noting that open-source does not replace copyright. And likewise, ==Legality of emulation==As a result of two landmark cases in the license cannot be removed after United States in the work has been released under early 2000s, itis considered legal to emulate any system. To see More specifically, the various open-source licenses availableruling was meant to allow commercial emulators to profit, see [https://choosealicense.com/ choosealicense.com]. Also see [https://choosealicense.com/appendix/ something Sony didn't like the appendix] at the same websitesound of; it's possible that if Bleem and Connectix hadn't developed commercial emulators, they wouldn't have been sued.

==SourceFree and open-availablesource software==The program fundamental concept of free and open source software is released under a copyright license more restrictive than an open-source license, but inversion of the source regular practice of software developers selling binary code is still publically availableto consumers and businesses. The biggest example is [[Snes9xsource code]], which is released under that goes into developing commercial software isn't open to the public because releasing it would give others a non-commercial licensecompetitive advantage and allow unauthorized ports. This license makes is what is known as proprietary software, named such because it not often has a proprietor (i.e. an owner). With free and open source software however, the source is open (hence the term open-source) and available to others to use, study, modify, and share, to ensure that a user always has access to these tools. The Linux kernel is at the forefront of the movement, as it restricts is the usersmost active open-source project. (It' commercial uses not the most widely-recognized, however; that would be Android and VLC Media Player.)

==Closed-source / Proprietary==The program's source code isnbenefit of software being open is that they't available. Often because the ecosystem behind the platform is closed, sometimes re easier to port to other platforms by nature virtue of being open (like Windows and Androidthough that says nothing about the effort required to get it working without bugs). Many of the [[Recommended Emulators|best emulators]] use an open source license, or sometimes by force (like every modern console)though not all of them do.

===FreewareDefinition===The meaning of open-source code isnis usually lost on those who aren't available familiar with it, but the institutes and organizations have defined what it means for clarity's sake. Essentially, a program is still considered open-source (or if you're a GNU advocate, free.software) when it grants the four freedoms, that it can be:

# run at any time.# studied and modified for any purpose.# distributed to anyone, and# improved by anyone. There's also copyleft, which is a play on copyright that inverts its goal of consolidating ownership to one entity and preventing others from having it, by ensuring that the ownership is largely in the public and no one can't have it. The copyleft strength of a license depends on how strict it is about keeping things open; weaker copyleft licenses require attribution but not much else, while stronger ones require the source to be available by any means necessary. The GPL is an example of a strong copyleft license; the BSD and MIT licenses are examples of a weak one, which makes it a frequent point of contention in the community which is better. Essentially, it's the difference between Creative Commons' Attribution and Attribution-ShareAlike license. One is the all familiar royalty-free license used by renowned composer Kevin MacLeod, the other is one of two licenses used by Wikipedia (they dual-license it under the <abbr title="GNU Free Documentation License">GFDL</abbr> too). ==Shareware / Trialware=GPL===A limited demo The GNU General Public License (GNU GPL or just GPL) is one of the most popular open-source licenses in the free software community, and for good reason; it's remained one of the strongest copyleft licenses, requiring users to share their contributions (some might say to an insane degree). The GPL has two widespread versions; version 2, written in 1991, and version 3, written in 2007. No one talks about version 1 (1989). The GPL3 was meant to reconcile license compatibility, address software patents, license violations, nullifying DRM by calling it an ineffective technological measure, and the big one; [[wikipedia:Tivoization|Tivoization]], which was a severe flaw they completely missed when drafting the first two versions that allowed Tivo to make use of GPL2 software by sharing its code while preventing unsigned firmware from being loaded on the program hardware. The GPL3 prohibits this, which proved to have major problems when Hyperkin tried to incorporate the GPL3-licensed [[RetroArch]] in the [[Retron5]] (among other violations). ====LGPL and AGPL====The GPL is not the only license that the Free Software Foundation created; because the GPL2 ended up being overly restrictive in how software could work with it, many open-source libraries needed a less strict license to allow interoperability with commercial software. This ended up being solved in two ways; the linking exception found in GNU Classpath's GPL2 license allowed it to not affect the software it would be bundled in, and the Lesser GPL, which is an entire license that was made to make this aspect clearer rather than be an exception. The GPL also doesn't account for software used exclusively for consumer-facing servers, so the Affero GPL was made to require web app developers to share the source code of their app to users over the network. ===BSD===The history of Unix is freecomprehensive but, to make a long story short, the Berkeley Software Distribution (BSD) was basically one of the many flavors of Unix that was very simple and permissive in how it was licensed. Ever since then, descendants like FreeBSD, OpenBSD, NetBSD, and DragonflyBSD have been licensed under a variation of it. The ISC and MIT licenses are based on its philosophy which makes them very compatible. The original license had four conditions: # Redistributions of the source code must retain the copyright notice.# Redistributions of the binary code must be able to show the copyright notice. # Advertisements surrounding the use of the code must have this line: "This product includes software developed by (organization)."# Do not claim the original developers endorse the use of the software without permission. The third clause (about advertising) ended up being controversial and was common left out of newer licenses, resulting in the familiar three-clause BSD license. FreeBSD and NetBSD removed the fourth clause as basically no one violated that clause, and OpenBSD used a version of the license that details the first two clauses in one paragraph instead of listing them in asterisked bullets. The fact that the licenses are so permissive allowed Sony and Nintendo to use FreeBSD in the PS3, the PS4, and the Switch without having to share the source code. The conditions in the BSD license are easy to modify, which makes it an attractive target for those wanting to include the prohibition of commercial use. [https://github.com/mamedev/historic-mame/blob/master/docs/license.txt The old MAME license] (and by extension [Intel CPUshttps://github.com/barry65536/FBAlpha/blob/master/src/license.txt FinalBurn Alpha] and [https://github.com/finalburnneo/FBNeo/blob/master/src/license.txt FinalBurn Neo]) is based off of (or was heavily influenced by) this license, which ended up causing a ton of problems in recent times, notably when a libretro port of MAME tried to backport GPL code into old-licensed code, and when the Capcom Home Arcade [[Emulation Boxes|DOSemulation box]] gameswas said to use FinalBurn Alpha ahead of its release (despite its creators not getting permission from all of FBA's developers). ===Apache===The Apache 2.0 license differs from both the BSD and GPL licenses in that: * It's not as permissive as the BSD because it still requires companies to state any changes they made.* It's not as strict as the GPL because it also prohibits trademark use. ==CLA (Contributor License Agreement)==Some projects use a Contributor License Agreement, which contributors have to sign before getting their work merged upstream. The sole intention of a CLA is to consolidate control of a project to one entity (which, as stated earlier, can be a person or a company). This can be useful if one wants to relicense the project retroactively when there are potential conflicts, but it's also a very easy way to prevent future versions of the code from being available (two projects in the Dreamcast scene encountered controversy with this approach). ===Dual licensing===CLAs allows emulators (and pretty much any work, even things that aren't [[source code]]) to be licensed under multiple licenses. Most often, the point of doing this is to allow a revenue stream that funds development of software and allows the primary developer to sell the software (or monetize it in some other way) without having to share the code (provided they pay a fee). At least, that's the most common use; one other is to allow the software developer to use the code in their own commercial projects. <!-- todo: gpl2+ ==Problems==todo: explain problems with copyright, license problems, and law trolls illegally registering trademarks and tormenting related projects. ==FAQs==todo: answer questions like "can a license be revoked after it has been put in place?" and "is it possible to sell open-source software?"-->[[Category:FAQs]]