The maybe most prominent and fully FOSS fork RedEclipse is still working on the promised new 1.4 release, with them doing some silly and some cool enhancement projects in the meantime... so yeah:
Red Eclipse in Valve Time tm |
Kelgar Gameplay 0.8 - Indie DB
According to their github page, content seems to be libre (CC-by or CC-by-SA) but information is a bit scarce. Even less information is available for this other fork, called SabiCube, but you can download and test their alpha.
Oh and a bit older, but also interesting: the emscripten powered HTML5 port of Cube2, called Banana Bread, has also really picked up since the main emscripten developer was hired by the Mozilla foundation. Here you can see it running a multi-player game (very recent new feature), and with the upcoming (also Mozilla powered) asm.js Javascript speed-up, it will probably run at near native speeds in the not too far future.
Ok... I hope that is all... if you know of other interesting Cube2 powered projects, please comment below!