GPL-Style License w/ A Twist?

txsable asks: "I'm trying to find out if there is a GPL-style Open-source license available with a special twist: that any modifications made, while being allowed to be released as per the terms of the 'normal' GPL, must also be submitted back to the original author for possible inclusion in the main project. I know it seems ridiculous to require by license what should be a common-sense procedure for open-source developers, but I've seen enough projects which were greatly modified from the original project, with features the original project either was working on or had also developed, and it led to confusion and/or unnecessary duplication of effort. Anyone have any suggestions for me (other than writing my own license...I don't speak enough lawyer to make something that reads as bad as a legal document)?"

Bad Idea.

[rjh]

1. This would violate the Free Software Foundation's definiton of Free Software. One of the primary freedoms of Free Software is the freedom of privacy. Namely, the right to keep your modifications private, for yourself, and not share them with your neighbor. RMS would certainly prefer that you do share--but he feels it unethical to require that you share. If you do this, then your software, while still being Open Source, will not be Free Software.
2. Think in the long-term. What happens in ten years when you're no longer active in the community? What if nobody can find you to send you these diffs? In that case, your software cannot be modified and distributed--because without sending you the diffs, the software cannot be distributed!
3. If you have a clause that says ``you are not required to send me changes if you can't find me'', then people can make whatever diffs they like and not send them on--after all, hey, they looked around their cube for you, you weren't there, so they just went on with business as usual. Yes, that's an extreme case, but it'd be technically legal.
4. The more complex a legal agreement becomes, the easier it is to subvert. The GPL is already on questionable legal ground; if you add another clause, even with a lawyer's help, you also diminish the likelihood that you can ever enforce this license.

... I don't mean to burst your bubble here, but this is just a Bad Idea. Better to leave a note in the README that says ``please, please, please remember to send me diffs'' and not make it a legal requirement of the license than to try and write in your own clause.

APSL

[Pathwalker]

You might want to check out the Apple Public Source License [apple.com]
It is pretty close to what you want, although it is not GPL compatable [gnu.org].
If you are writing your own, it might be a useful starting point.
There is a nice list of other licenses here [gnu.org] - always a good spot to start exploring.