I've had extensive talks via email with Stenzek aswell as several of his contributors. I won't publish those emails without permission, but it got quite heated indeed.
Some of them weren't too happy, but an equal number of them confirmed my suspicions: DuckStation is violating the GPL with its recent change.
I have nothing against Stenzek personally. He's an extremely intelligent and skilled young man. Passionate. He will be free to contribute to my new project when it launches.