Modifying an open-source license with optional requests

Question

A general question about open-source licenses: I know you can't modify them yourself (i.e. "GPL except you can't do this") and writing your own is generally a bad idea. However, is it feasible to add "Please do this" riders?

For example, say that I want to license something under the GPL. Can I add a clause which says "If you release a fork of this software, you are hereby requested to contact so-and-so and notify them"? Would this count as a different license? For that matter, is the license even the right place for such a request, or should it go in a README (and if so, how would you get it to propagate)?

Edit: To clarify, I'm primarily asking whether this is something that can be done, and only secondarily whether it's a good idea (I suspected not, and the first responses confirm it). I have no intent of actually doing so, it's just inspired by an unrelated discussion I had.

Answer 1

I am not a lawyer, but

don't put such things in the license, which is a legal document to be mostly read by lawyers.

^{Avoid changing a single byte or sign in legal documents. You are probably not a lawyer neither.}

Notice that the legal text of license is usally not open, in the sense that you probably are not allowed to change that text (and still call the license by its original name). Also, common licenses (like the GPL and many other OSI approved licenses) have a well established understanding (some lawyers, at least in big corporation, already know them). In some big organizations, people might be forbidden to use any nearly free software with a bizarre license.

Just put such a wish (it is not legally binding) in the README file. Better yet, put your source repository on some widely known forge (like gitorious or github etc...)

BTW, such requests are not mandatory. But in practice, you'll have few downloads at first, and you should be very happy if someone fork or contribute to your project.

Also, by releasing your software you should put some trust on the users and you are requiring trust from contributors (and users also). So be nice, and expect a priori other people to be as nice as you.