I am not a lawyer but previously in my career I dealt with software licensing and FOSS. When it comes to charging for FOSS it is almost always for support. Otherwise you are 100% on your own to read documentation and figure out how to use it.
I am not surprised at all by their reaction and request for you to pay for the software when calling for technical support. This is their business model, make money off of the tech support.
Most of the people I work with in tech (FANG) can barely speak to another human. This must be what non-tech thinks it’s really like.