[smhenderson]

As to your question, you've already agreed not to charge for your patch by the fact that you've utilized the GPL to access the code in the first place.

Nothing about the GPL stats that you can't _charge_ for your software, in fact RMS explicitly encourages people to make money from free software. You just can't restrict the buyer from redistributing it once you sell it to them.

[mark-r]

True, charging not explicitly prohibited. But since everybody you distribute to is free to redistribute it again without charge under the terms of the license, it does put a practical limit in place.