To give my 2 cents, again:
Roundcube just switched from SVN to GitHub. Look at the project page at https://github.com/roundcube/roundcubemail
. It has a ton of watchers and a few forks already (about 10 days after the switch).
As soon as my own projects reach v1.0 I will try to contribute to Roundcube and ISPC more.
One (maybe dumb) question:
Is there an equivalent to GitHub "pull request" for SVN?
For me this is one of the great features of GitHub. Everyone can contribute and the maintainer can check all commits before merging the code.