OpenArena uses icculus.org/quake3 as an engine base now. The diff file for the changes needed is provided. The engine source can be obtained from here:

http://svn.icculus.org/quake3/trunk/

The binaries are compiled at revision 1107

NOTE:  You may have to manually apply the changes to --- 

code/server/sv_client.c
code/client/cl_main.c
code/qcommon/files.c
code/qcommon/qcommon.h
code/ui/ui_main.c
code/client/snd_dma.c
code/client/snd_openal.c