Cygne is an open-source WonderSwan/Color emulator. It was the first ever publicly released WonderSwan/Color emulator.
The official website of the Cygne emulator was last updated on March 26, 2002, so this was definitely a very ancient emulator by emulation standards. The last version of Cygne, 2.1a, was updated on March 12, 2002. Cygne was originally developed in beta form for the DOS but has since then been improved and several issues fixed such as better timing and the SRAM. In the early 2000's, it was reputed to be one the best WonderSwan/Color emulators - but Cygne isn't recommended today in the advent of more advanced and better alternatives.
The NEC CPU emulator code was taken from the MAME project.
It was, in the early 2000's, a very good WonderSwan emulator. It emulates WonderSwan Mono and Color, has a nice GUI, and good sound. It is based off the Cygne source code and authored by David Raingeard. This was an unofficial continuation of Oswan by PmHacks (Later called Normmatt, who did several English translation patches for GBA games) that improved sound and performance. Oswan also features the ability to apply several video filters as well as color schemes to add color to WonderSwan Classic titles. The source code is also available.
The latest Oswan branch can be found at the OSDN webpage. It says that it is written in the C++ programming language. However, that branch seems to be old as the latest version, 1.73, was uploaded on January 23, 2007, while OswanJ r99 (Japanese language menus) was uploaded on June 08, 2010.
- aep emulation page (German language site. Downloads of various branches of Oswan, including an old Mac version and the Japanese and German language editions of OswanJ.)
- BANDAI WONDERSWAN 101: A BEGINNER’S GUIDE (July 6th, 2007 by racketboy; updated June 19th, 2018. Old feature covering early WonderSwan emulation. Oswan and WSCamp were the recommended emulators according to the article.)