I had the same feeling when I read how they told Mark to keep the laptop.

I wish you guys all the best and hope this gets sorted out soon.

I get the whole leaving on good terms, really. But this whole "hey, we just want you to keep the code and answer questions for our other engineers" aspect really ought to have set off red flags.

Pro-tip, hand write a nice letter to your boss/colleagues on your way out. Bingo, no burned bridges, and no risk of law suits for holding on to company IP.

Yeah, I hear you, hindsight 20-20.

It was Mark's manager John Shimmin who made that request. John is a great guy, and Mark had (still has?) a great relationship with him. He genuinely wanted to help Shimmin, and did so faithfully for weeks.

It's not fair to pin this on Mark and dismiss it with a "rookie move dude." Mark (and I) had no idea that facts could be twisted and ignored to create this kind of legal conflict. A lot of people operate under the guileless belief that if they help someone, that person/entity will not screw them. Mark is one of those people.

Unfortunately, the 'rookie move' is a fair assumption. Even if there was a small possibility of conflict: Your IP is your company and these things should have been covered.

It's a sad lesson and an emotional mistake. You didn't owe the employer/managers anything and should have cut all ties to the company especially since these projects are somewhat related.

You are both good guys for wanting to help out and it sucks that things got twisted up. I hope things work out well and I wish you all the best.

Hand written with a pen? From the perspective of a millennial I am curious about if it is more polite to email or hand over a written letter.

I suspect this may significantly depend on the quality of your handwriting. I'm just old enough to believe that handwritten is more polite in theory, but in practice I'd probably send an email, or print out a typed letter and then initial it.

They can't tell if I was being nice if they can't read what I wrote, after all :)

Yes, handwritten with a pen. Bonus points for nice stationery. Extra bonus points for using a fountain pen.

Print out and hand it to them in person. Hand written in pen isn't needed but email is way too impersonal in my opinion.

When I left an employer to found a startup, I didn't say a word. Just said I was leaving for another position, gave notice, and left normally.

I agree: rookie mistake. This is particularly true given that there's at least some market overlap (video, etc.) and the CEO gave a talk where he basically threatened employees.