No Linux, no sale. Krita's been on Linux since 1998.
That aside, it looks like an awesome product, good work so far. I like the focus on super fast and smooth operation; that's why I use Sublime Text :)
Leonardo use as little OS specific stuff as possible to make porting easy so going from Windows to Mac (and maybe Linux in the future) shouldn't be that hard.
Thanks. Sublime Text has been one of the many inspirations for Leonardo! :)