Someone already mentioned MySQL, which is one of the most famous projects to take advantage of GPL copyleft. If you want to distribute it, either you contribute back your changes (participate in the open source community) or you buy a commercial licence.
And GPL has a track record that includes being enforced in courts. I'm not sure that applies to any of the attempts to write a licence that says "free for non-commercial use". Such clauses can beg questions like defining non-commercial use, and are sometimes associated with unrealistic expectations.