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>>102541313
The problem here is the lack of "consideration". Every single contract between two willing parts depends on
1) mutual consent (no forced acceptance)
2) perfect understanding of the terms (no "fine print")
3) consideration

The later is obvious but tricky. A contract there one party is obligated to provide "money" while the other is obligated to provide "not burning your business to the ground" is clearly extortion, not a valid contract.
In this case you're linking, the "consideration" OpenAI is offering is
>not reneging on a promise made when you were hired
and that's obviously illegal.

Usually Non Disparaging Contracts offers a lump sum that would otherwise not be paid in return for the person not badmouthing they company after they leave.
It is usually very enticing but completely voluntary and some people went on record saying
>I left 30k USD under the table for the privilege of making this tweet: company such and such CEO is a poo poo head
or something to the effect.