"Most of the people who played both Counter-Strike on
Windows (or through Wine) and Urban Terror usually have the same
opinion when describing it: it's like Counter-Strike, only better.
That was my impression too. I think Urban Terror is the best
alternative for those who like CS and eventually made the switch
from Windows. It is natively supported on Linux, it is maintained
constantly and it has a solid community. In fact, when I first
played it about a year ago, I was stunned to see that I was playing
it very good just because I was used with Counter-Strike.
"Developed by Frozen Sand, the team behind it, Urban Terror was
initially developed as a Quake 3 mod, but the game offers now a
complete package and can be run without the need of Quake 3
binaries. The last version, UrT 4.1, comes with a ZIP package for
Linux, of about 700 MB, and you only need to uncompress it, make
the ioUrbanTerror.i386 binary executable and run it."