Mikmod is a module player and library supporting many formats, including mod, s3m, it, and xm. Originally a player for MS-DOS, MikMod has been ported to other platforms, such as Unix, Macintosh, BeOS, and Java(!!)
libTiMidity is a MIDI to WAVE converter library that uses Gravis Ultrasound-compatible patch files to generate digital audio data from General MIDI files. This library based on the TiMidity decoder from SDL_sound library.
Cross-platform reimplementation of AMOS BASIC (runtime)
XAMOS is a cross-platform reimplementation of AMOS BASIC based on jAMOS, fully re-written in C++ with SDL libraries.
Currently runtime only, however is widely compatible with jAMOS projects.