You can do pull requests through github, but Subversion is still preferred. Things aren't integrated; so for example if you look at https://github.com/ruby/ruby you will notice Issues is not enabled; instead you have to go to a separate issue tracker over at https://bugs.ruby-lang.org/projects/ruby-trunk/issues.

I still contribute, but the barrier to entry is higher; people have to hunt the ruby home page to find this information which is not ideal.