I recently saw that people on Ubuntu 13.04 (Raring Ringtail) have Krita 2.6.3 in the repository, while I on linux mint 14 only have access up to 2.6.1 (kubuntu backports and the beta releases channel).

Is this the Ubuntu packagers having funny naming scemes, or is Krita 2.6.3 already out? And if so, what is the best way to aquire it?

The latest version is 2.6.2, usually newer versions are available as ppa see http://krita.org/download

Doesn seem to be the case at the moment though.
I have the kubuntu backports ppa activated, but my version of Krita claims to be version 2.6.1