As reported on clan-x-treme.de the development of the Q4 X-Battle (XBM) modification has ceased.
^CHAMPi^: "There were 2 reasons for this decision. First of all is that kaffeedoktor left the team to join up the Q4MAX team. He was the most active part of XBM and spent hours of development in XBM each single day! So with his exit the team lost a lot of his coding force.

Secondly, and that's a really important point from my side of view, i lost the interest in Q4! Which means that i didn't play it any more (at least not at the moment). So, it didn't make any sense for me to develop a mod that i didn't play."