It is important to note that they don't prohibit commercial development on the community edition.

They just do not promote the community edition for commercial development.

I, for instance, could choose to use PyCharm community since I rarely use any of the tooling that comes with the 'pro edition', but when I do need something---like Cython debugging---its damned useful.

Depends on how you define commercial development.

You can certainly do commercial applications using Intellij IDEA CE, if you don't need Java EE, Spring, GWT, Grails, etc deep integration in the IDE.