Our Sourceforge project is now upgraded.
The old SVN URL is now a read-only repository, and everyone should witch to the new one, which is at:
svn+ssh://svn.code.sf.net/p/caveman2cosmos/code/trunk
or
https://svn.code.sf.net/p/caveman2cosmos/code/trunk if you prefer to use https
Sourceforge's recommendation is to do a fresh checkout to a new folder an start using that. It **may** be possible to change the URL in the repo browser on your existing folder but I haven't tried, and it's quite likely it won't work due to out-of-step databases.
As a result of needing a fresh checkout you'll need enough disk space for another copy (once you get it all working the old one can be deleted of course, though I'd recommend doing that after you get the new one working unless you absolutely need the disk space freed up by trashing it first), and have to download everything again, so it's a slow process I'm afraid.
Mine is currently in progress - I'll let you know how I get on...