Indeed, on source forge, it is distributed with CVS and it is indicated this :
SourceForge only supports read-only access to CVS now. For more information see our blog post about decommissioning CVS commit support. If you are a project admin, you can convert your repository to SVN or Git with these instructions.
Moreover, almost no improvement has had an owner since the end of 2016: Feature Requests, and no updates have been sent to CTAN since 2015.
So, what is the future of pgf/TikZ?
git clone git://git.code.sf.net/p/pgf/git, so moving a copy to GitHub (or linking a GitHub repo with the SF) should be very easy now. Things are moving ;) – Kpym Apr 30 '18 at 11:52