Jagged Alliance 2 is one my alltime favorites anyway, so my vote goes to its forks v1.13 and ja2-stracciatella.
(both based on the official ja2 source, ja2-stracciatella = with a vanilla flavor, v1.13 = adds loads of new stuff).
Both of those still going I think? Not bad considering the original came out in 1999.
Another really awesome one that comes to mind is re3 (GTA3/VC port), although that one is a sad sad story.
I say sad because the legal status of this project will probably never be "kosher" as they say.
The source was painstakingly recreated from the binaries and then recompiled, with the end result that's already as good or better than the original.
Yeah before you ask: I'm sure someone, somewhere is already doing the same with the later ones in the series...
Btw a "port" as I understand it here is "(mostly) the same thing, running on a new (different) platform".