MyPaint download page (http://mypaint.org/downloads/) says:
“We maintain an Ubuntu PPA which is a rolling build of the “master” branch on GitHub. We try to keep things on the master branch fairly stable and tested, but there are bound to be bugs.”
Actually, all of the packages on that PPA are for outdated Ubuntu versions.
I don’t think anyone other than @achadwick has access to that ppa(?), and while we could create a new ppa with a higher bus-factor I personally have no experience creating deb packages.
I have no experience in this area myself, but if anyone wants to try to pick this up, I’m sure our Ubuntu/Debian users will appreciate it!
The relevant repos for the deb packages are these: