[kemitchell]

I lead a project to develop a strong-copyleft license that makes development tools "free for open source":

https://paritylicense.com

The idea was that developers like you could make your tools available under Parity and charge folks who want to use their code to develop closed, rather than open, software. However, several projects and companies have also used the license simply to make sure their work stays open, without selling any permission to build closed projects.

[seanwilson]

I like the idea. How would it stop someone releasing a free version of a paid development tool though? It relies on people downloading the free tool to be honest enough not to use it on commercial projects?

[kemitchell]

No license can guarantee compliance with its own rules. That's true of all copyleft licenses, including GPL, EPL, and MPL.

Whether and how to enforce the license is up to the developer.