I'm trying to run nexuiz using the branch "nexuiz-2.0" on SVN.

If I do so, then I get this silly error

"You have reached this menu due to missing or unlocatable content/data"
"You may consider adding -basedir /path/to/nexuiz to your command line"

How may I fix this?

You need to compile the game code and menu sources with a QuakeC compiler. We use FTEQCC. Go to data/qcsrc/server, invoke fteqcc. Then go to data/qcsrc/menu and invoke fteqcc.

Then things should work.