> when is Java and its related framworks the best choice for a side project/small group endeavour?

If you want to use the project to learn a new language/framework, go ahead, but if you already know Java and you just want to get the project done, use it.

And while typing doesn't matter so much for many applications, static typing can save your ass as well as provide a guide for integrating with libraries. My experience with Django was good, but I found myself diving down into the source of both the core and of other "apps" in order to get the interactions right. With a java application, you almost never have to do this.

Generally, though, you should use the language/framework you know, as long as it isn't PHP.