This section is directed to commercial developers considering incorporating software that falls under one of these standard licenses into closed-source products.

Having gone through all this legal verbiage, the expected thing for us to do at this point is to utter a somber disclaimer to the effect that we are not lawyers, and that if you have any doubts about the legality of something you want to do with open-source software, you should immediately consult a lawyer.

With all due respect to the legal profession, this would be fearful nonsense. The language of these licenses is as clear as legalese gets — they were written to be clear — and should not be at all hard to understand if you read it carefully. The lawyers and courts are actually more confused than you are. The law of software rights is murky, and case law on open-source licenses is (as of mid-2003) nonexistent; no one has ever been sued under them.

This means a lawyer is unlikely to have a significantly better insight than a careful lay reader. But lawyers are professionally paranoid about anything they don't understand. So if you ask one, he is rather likely to tell you that you shouldn't go anywhere near open-source software, despite the fact that he probably doesn't understand the technical aspects or the author's intentions anywhere near as well as you do.