Krita is an open source graphics app with the emphasis on drawing & painting that I think some may appreciate, given the popularity of Twisted Brush etc. It comes with a setup app or as a zip file -- the zip version is very nearly portable, with files added to User AppData Local & Roaming folders. It does add logs for peer networking so you might want to check the app's option settings -- I really haven't had much chance to play with it yet, & the way I'm feeling it might be some time before I do, so wanted to get this posted so others could have a look if they wanted.
The Krita site is krita[.]org, & in case that's down [it was earlier], kickstarter[.]com/projects/krita/krita-2016-lets-make-text-and-vector-art-awesome/posts/1594853