As long as people can still write plugins and exporters for it, it sounds fine. I personally don't care about if the editor's open source or not, but I can understand how users of other platforms would be disappointed since there's been talk of making a cross platform port using qt. Since I'm assuming moving C2 over to use qt isn't an option, I guess what matters to me is that you devs are able to make a living making construct.
What I don't understand though is why you can't have it be open source and put license restrictions/require royalties on making exporters. Even if it's closed source, as long as people other than yourselves can write exporters for it, people could still write a free version of one of your paid exporters. You could send a cease and desist, but how would it be any different from it being open source with a license that prevents it and the same thing happens?