Who would sue, and on what ground?

They basically gave stuff away for free and now they're speed-running enshittification. The end state will be an abusive, adversarial, fully monetized, vendor lockin experience like Oracle or Broadcom. Nobody is forced to play.

Switching costs are still low. Anthropic can only do this while they maintain frontier status, and while they do, they can charge whatever they want. An Oracle or Broadcom would fall behind and lose all its customers in an instant.