I think that free in this context has to be interpreted as "free as in freedom" and not as "free as in free beer".

You can still support the authors by donating and/or buying licenses, services/consulting or support.

This is "Free" as in "Libre" / "freedom".

Free as in freedom. Not price. You can ask any price for distribution of the software. You can ask any price for support. The software just has to come with the 4 essential freedoms.

Free as free speech not free beer.