It's reasonable to ask for a cut on your software output, if the author is giving it out for free. While should they give out their work for free to people who are going to make money out of it?
Actually, asking for a cut could become a standard option for selling software where you would offer at customer's choice:
- GPL;
- commercial license, paid upfront;
- commercial license, paid by royalties.
That way, people who don't agree to the GPL, but still think your commercial license is too expensive compared to their expected earnings would have a further option: no gain, no pain.
As a side note, one of the reasons I prefer software which comes with standard licenses (GPL, BSD, etc.) is that I know what those licenses say, and I can click on "I agree" without worrying about the fine print. If the license text differs in some way from its template, authors are explicit about that.
Actually, asking for a cut could become a standard option for selling software where you would offer at customer's choice:
- GPL;
- commercial license, paid upfront;
- commercial license, paid by royalties.
That way, people who don't agree to the GPL, but still think your commercial license is too expensive compared to their expected earnings would have a further option: no gain, no pain.
As a side note, one of the reasons I prefer software which comes with standard licenses (GPL, BSD, etc.) is that I know what those licenses say, and I can click on "I agree" without worrying about the fine print. If the license text differs in some way from its template, authors are explicit about that.