He lives in Texas still

I really doubt Carmack would decide his life based on NDAs or non-competes.

There is when equity changes hands, which will have been the case with Carmack.

No. Everyone is given equity in Silicon Valley.

See x3n0ph3n3's comment upthread.

There is for C-suite employees.

They are actually permissable in circumstances similar to John Carmack's:

> California employers can sidestep non-competes in the following instances:

> EXCEPTION 1: If the employee sells business goodwill

> EXCEPTION 2: If the owner sells his or her business interests

> EXCEPTION 3: If the owner sells all operating and goodwill assets

> Upon the business’ dissolution, a member of the company may agree to a non-compete if operating a similar business in the geographic area. Goodwill is the company’s name and brand reputation. Employees with stock options are not considered company owners for purposes of non-competition agreements.

https://www.contractscounsel.com/b/non-compete-california