That is not true. It's released under the GNU GPL, which does not make a difference between commercial and non-commercial projects afaik. It only says if you distribute the binary, you also need to give away the source code and others may redistribute and modify it. That does not mean, however, that you can not run it on your own server and keep the source code for yourself.
But it's all bundled up, so you're linking: you need to give your code away. That's my understanding at least. If it were purely server-side, you'd be correct, but it isn't from what I can tell.
Also, the fact that they talk about commercial licenses is indicative that they may be thinking along similar lines.
As davidw says, you are distributing the "binary", because you are sending it to people's browsers in the form of javascript. Under GPL you are not permitted to do that unless you also make available to them the full source of your application.
Under a license that does not permit you to easily use it for commercial projects, unlike, say, Django, Rails, Node.js, etc... etc.... etc....