The source code is fully available, none of the features are paywalled. They only prohibit you from taking their code and reselling it.
If you take a look at the Play Store, there are thousands of instances where open source projects are lazily renamed and sold for $5 or $10. It's the definition of scummy, pathetic, worthless behavior, and I'm glad the license prevents those kinds of leeches from succeeding.
I know this isn't the only case, but it's the majority of cases. So I have no problem with their license at all.