Didn't the license prevent forks?

I think he claims he owns the copyright; if that's true, the license doesn't apply to him.

That's a bold claim when he was being paid a salary to work on it.

Was he? His claim is: "I have never had any employment agreement, copyright agreement, licensing agreement, NDA or even work contracts with Copperhead. There was a mutual understanding that I owned the code I was writing."

Work for hire doctrine says he has aa very poor argument.

Work for hire is a statutorily defined term (17 U.S.C. § 101), so a work for hire is not created merely because parties to an agreement state that the work is a work for hire. It is an exception to the general rule that the person who actually creates a work is the legally recognized author of that work. According to copyright law in the United States and certain other copyright jurisdictions, if a work is "made for hire", the employer—not the employee—is considered the legal author.

https://en.wikipedia.org/wiki/Work_for_hire

I can't think of a context where a judge looks at a salaried CTO commiting code to repositories with the same name as the company, in inarguably the core domain of the company, and shipped in the name of the company by said CTO, with nothing written down to the contrary and goes "oh yeah, that's totally his code, not the company's".

I think Daniel's in the process of learning that verbal agreements don't mean anything when the shit hits the fan. IMO that's what he gets for switching to a non copyleft license.