This is as ethical as it gets. They're getting compensated by being able to use the result of their work freely. This is the rising tide that lifts all boats.
Well, the frontier models aren't freely available in the same way that the training data (the public web) is; they're only available as a limited no-cost tier of a paid service.
There are models where the weights are released and you can run them locally, but one counter-argument I've seen is that these aren't really the models that people are excited about and making extraordinary claims about.
