However they could add this to new employee contracts.
Pushing unenforceable scare-copy to get employees to self-censor sounds on-brand.
Boomberg famously used this as an employment contract, and it was a campaign scandal for Mike.
People are different! You can think otherwise.
Doesn’t mean that that’s legal, of course, but I’d doubt that the legality would hinge on a lack of consideration.
In fact both of those seem quite bad, both by regular industry standards, and even moreso as applied to OpenAI's specific situation.
If it was "we'll give you shares/cash if you don't say anything bad about us", that's normal, kind of standard fare for exit agreements, it's why severance packages exist.
But if it is "we'll take away the shares that you already earned as part of your regular employment compensation unless you agree to not say anything bad about us", that's extortion.
But how is that even possible when corporations are typically run by ghouls who enjoy relativistic morals when it suits them. And are beholden to profits, not ethics.