I think this is a very good idea. Everybody uses Github nowadays and if Github got evil one day, it'd be easy to transition to somewhere else thanks to git. Even the Github pages and the Wikis are in the git repositories itself.
There's loads of abandoned stuff on http://dev.osdrawer.net/projects and OsDrawer sucks majorly, it's slow as hell and often enough doesn't work at all. So if you want to do the world a favor, you could use git-svn to "rescue" the projects from there. I guess it's a good amount of work though.
Oh and btw, it looks like the Redmine software on OsDrawer hasn't been updated in a very long time. So I wouldn't be surprised if it'd suddenly be gone some day, which is another good reason to archive the stuff there.