Be careful, US companies usually have you sign IP contracts and do not approve of moonlighting.
They could well try to claim stake or ownership on your company, even if they lost, the distraction and money it would cost to defend probably aren’t worth it.
> They could well try to claim stake or ownership on your company...
Note that not only is this not legal in California (but is in others -- Texas is particuarly notorios) but any employment agreement in California must specifically include a copy of the relevant section of law so that the employee is a aware of their rights. But don't use any of the employer's property (e.g. computer, IP) or do it when you are supposedly working: in that case the law does not apply and the employer does get the rights.
If they hire as a contractor, then it's easy to say no to these clauses.
If they hire through a local subsidiary then these clauses are against the law in much of the Europe.
How the hell can they justify this habit of telling a developer what they can and can't work on in their own time, or making any claim to it afterwards just because someone worked at company X during the same time they made side project Y? The whole tendency seems grossly onerous and unjustifiable to me.
Then why is there no widespread pushback against this idiocy? It's grossly unfair and seems like a lite version of some notion of serfdom, by which you belong to your emplo0yer just because you spend part of your day working for them during some time period.
They could well try to claim stake or ownership on your company, even if they lost, the distraction and money it would cost to defend probably aren’t worth it.