First off, a share in what? Is this assuming that, like most startups seeking investors, the company is formed as a Delaware corporation? Or do you want something more along the lines of a partnership agreement, to use before any of the founders form an actual entity?

The form of this agreement would heavily depend on the context.

I'm a neophyte here, but I don't understand what that means. Are you asking past YC founders to release a short statement regarding "starting-up understanding"? And what are cliffs?

Yeah, basically, if the shift founders had signed a 1 page non tremendously complex statement saying that there is a 1 year cliff and this is what happens if someone isn't there (An advisor share for example) there wouldn't be a lawsuit at the moment.