From other articles[1] it looks that way. Really makes you think how big github has become.
[1] http://www.theregister.co.uk/2015/01/15/codeplex_repository_...
[1] http://www.theregister.co.uk/2015/01/15/codeplex_repository_...
As a social-networking website, the most important thing that defines it is the number of users. You could publish your code on Codeplex or Bitbucket, but you would be simply limiting your reach.