There was a time when Brushes (the other app from this developer that also just went open source) at least seemed to me like the best known and most popular painting app on the iPad. It seems to me like there should be money in this, even with minimal work. Or at least he could have sold the apps to someone.
There is just no explanation as to the reasons for this step anywhere. At least I couldn’t find any.
Edit: Ok, I think I figured it or at least something out by looking at the release history. The app was last updated more than a year ago and only minimally to add iOS6 support. The last update before that was again a year back, in September 2011. Brushes’ last update is similarly already a year old.
Time really does fly, it feels to me like I was using Inkpad just recently and that is was very much actively developed. But it seems like the developer had just very little time and in this context this seems like a pretty awesome step. This is definitely preferable to letting the apps rot in the app store (especially considering that those are pretty damn great apps).
It’s definitely a great way to continue working on those apps and keeping them alive without putting quite so much time into it, albeit without getting paid.