OK, that shouldn’t cause an issue as long as you are positive that you are linking to the demo framework from the non-licensed apps and not the licensed framework.
Are you positive that you set the -ObjC “Other Linker Flag” in the target of the app that is having the issue? It looks like the RapidEars demo was somehow just not quite successfully installed by the exact steps in the tutorial. That is usually the step that would cause a method that is in the plugin to not work.