The converse of that is as a frontend developer pretty much 100% of what I use is MIT or similar licensed. In fact I'm struggling to even think of one software

The converse of that is as a frontend developer pretty much 100% of what I use is MIT or similar licensed. In fact I'm struggling to even think of one software package that is copyleft in the frontend world. I dunno, I'll admit this thread has been eye opening. The GPL is definitely more common than I originally thought. But I think really nailing down specifics on this would be tough.