I would seriously consider packaging this as an enterprise teaching tool for developers. Companies buy this sort of tools for training. Very good commercial potential here.
I also spoke to the Github guys about integrating this into their set of training tools (try.github and a few docs), but I think they got caught up with their full time responsibilities because I haven't heard back in a while.
I could commercialize it but it deserves to be free!
I'd be really disappointed if someone added one level and started selling a zip file of the application to enterprises for $400 a pop.
That being said, I've heard the GNU license is sometimes too prohibitive (albeit no definitive examples). If you know licenses at all, I'd love some advice
$400? This would sell for thousands in the right market. Add in training, and you have a long time gig here. This would even be a great online training business. So many possibilities.
Right now, you cant be disappointed if the license allows it. If you have doubts, change it now. In terms of licenses, I'm not really an expert. But you could just roll your own. Just take the one you have right now, and remove what allows people to sell it. Still won't stop some people from doing it, though.
For example, I forked your repo. Why? Because its such a nice platform, that I want to learn how it works. I saw that about other 20 people had forked it too. What is stopping them from putting up a website and selling it? Nothing. Nothing at all.
Open source is awesome and all. But you have to also be aware that there are a lot of ruthless people out there waiting for programmers like you to put out software like this one under such licensing terms. Its like buying a car, and listing everyone you know as an owner in the title. Can't get mad when they sell it.
I could commercialize it but it deserves to be free!