TBF there is a lot of things “free of charge” connected to commercial activity, e.g. Android, .NET Core, MongoDb, ElasticSearch, even RedHat with Linux …
I understand need to somehow include them, but the line should be at the for-profit companies and exclude non profits and individual developers.
How to formulate it without easy loopholes is no easy task.
The trick of course will be to have the software offered as a paid product by a non-profit, while having a for-profit outfit develop the software as a custom/consulting engagement for the non-profit. You can thank me later.