Hammer of Thyrion (uHexen2) is a cross-platform port of Raven Software's Hexen II source. It is based on an older linux port, Anvil of Thyrion. HoT includes countless bug fixes, improved music, sound and video modes, opengl improvements, support for many operating systems and architectures, and documentation among many others.
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.
FreeMAX is a M.A.X.: Mechanized Assault & Exploration mod that allows you to play M.A.X. with the Stratagus engine, as opposed to play it with the original M.A.X. one. So you need to have a legal copy of M.A.X.(original DOS Version required).