I don’t think much has changed from the last Refraction discussion from a few years ago. That thread also has references to ArtPaint and Stephan also mentions that he wrote Wonderbrush because Refraction and ArtPaint and Becasso did not properly handle alpha blending. Probably trying to continue Stephan’s work on Wonderbrush 3.0 would also be fruitful. I don’t think we need more open sourcing of abandoned projects, we need people to work on the ones we already have the code for.
I intend to mess with Wonderbrush 3.0 when I get a chance but I have a long list of such things I want to mess with…