It can be done -- I am now able to do cvs ops on SourceForge from both my home and from work. You follow their directions, wait 12 hours or so, set your private key file for no passphrase (ssh-keygen -p), and it just simply works, for me at least.
The biggest issue is getting the public key to them in that little text box with no carriage returns in it. Then, of course, you have to wait.
I am mirroring the cvs for acs3-pg and driver-2.3 nightly thanks to this.