The title of the bug really says it all. Quakeforge still depends on virtual/x11, though it shouldn't. Libraries needed appear to be (based on perusing the configure.ac file): libX11 libXext libXxf86vm (can be disabled) libXxf86dga (can be disabled) Note that as a workaround, if you have USE="-X sdl opengl" you'll still get the "sgl" clients, which work IMHO better than the native X gl clients anyway.
I always forget to include the package version...
Fixed in CVS. Thanks for the bug report and the fix.