If you incorporate GPL'd code into custom software, the only people who are entitled to the source code of the program are the entities who receive the binary of the program -- not just anyone who wants the source.Wrong. Have you read the GPL? See section 3b. If you do not distribute the source to the recipient of the binary, you must provide offer valid for any third party to request the source from you. So yes, other folks can very well be entitled to the source code of the program under the GPL if you don't give your customer the source up front.