Ask HN: Licensing a CSS Framework

Hey HN, I have been developing a CSS framework for quite some time, and it is almost ready to launch.

Ideally, I would like to earn money using it, but don't really like going the ads and sponsorship approach. So I was thinking something like this:

- The framework is completely free (with source available) for usage in free and commercial applications.

- If someone wants to extend it, and sell those assets (specifically themes and templates), a commercial license needs to be purchased for a tiny amount of money, paid once. Not a subscription.

Does this make sense? Would I alienate developers by having this structure of licensing?