VT is something like a engine remake for the TR game series. If you don't know what TR is, then here are some tips:
I don't say names here, as this might be an copyright infringement. I also won't tell what VT stands for, as it's just a stupid playing with words.
The code is licenced under the GPL. As the game data is taken from the original games, there is no game data included and thus doesn't have a licence.
Will hopefully come soon...
I currently don't plan to do any binaries now or in the future, as this might get me into legal problems which I want to avoid. I will make source releases in the future, but for now you have to get it from CVS:
cvs -d:pserver:email@example.com:/cvs/cvsroot login
(password is "anonymous", without the quotes.)
cvs -z3 -d:pserver:firstname.lastname@example.org:/cvs/cvsroot co vt
You can find some documentation here and there is some doxygen generated documentation.