Beats of Rage is a homebrew freeware video game made by Senile Team and inspired by the classic Sega Streets of Rage game - a retro-style sidescrolling beat-em-up game. It was originally written for DOS, but all code was written from scratch and with porting in mind - so the source should be OK (especially since there's a Linux binary anyway). It's quite a popular game - especially with all the mods out there! A treat for anyone who misses the type of fun Golden Axe, Double Dragon and similar games provided. :] (There is also a "fork" from it called OpenBOR.)
The OpenBOR ebuild is in bug #136470.
I guess this is obsolete now that upstream appears to no longer distribute BoR and there's a bug for OpenBoR.