Welcome to Xonotic! At this moment servers are mostly empty, since Xonotic is still in a rather early development stage. You will find players online at some time or another, but a good way to find someone to play with is joining #xonotic.pickup at the quakenet IRC network (see also
this thread for more information).
Also I experienced that just joining a server near to you and waiting for a while can attract other players, so that form of "volunteering" can be successful too.
I read developers talking about a 0.2 release being in the pipe (already collecting credit information from the contributors... must be rather serious about releasing 0.2), so there'll be more players online probably when that release is out and announced on the relevant communication channels.
In the meantime I recommend you to use the autobuild available
here, if you don't use that already. The 0.1 preview build is way outdated and almost unplayable on servers using current git or autobuild version.
In any case, this project is far from being "dead". We only didn't have any official release yet that would be more than a mere preview. I suspect the 0.2 release or whatever version number will be assigned to it to receive a lot more medial attention than the 0.1 preview. Stay tuned! :o)
Edit: haha I just saw that you already joined #xonotic.pickup but left again - let me just hint that most games take place on that channel in the evenings european time currently due to a lack of Australian/North American players. But we do have some NA players there as well hoping for a game to take place at convenient times for them so don't be afraid to add up if you want to play :o)
