Not sure an ipad version could be possible, because of how the apple store and the gpl are incompatible.

Right, the GP comment should be: "I wish there were an iPad-quality tablet that ran GNU/Linux" (which I too wish for)

End users can compile iOS apps from source and install them without paying the developer fee. It could be distributed as source.

They would have to rebuild (re-sign) and reinstall weekly. The opposite of Just Works.

if you use krita for painting, artstudio pro is a pretty good alternative. i've found it does pretty much everything i'd want out of photoshop & also has .abr support. the biggest downside so far is that it eats through battery much faster than any other ios application i've tried.

Well in their GSoC ideas there is an idea to make Krita work for Android/iOS