[mathgeek]

The "founder" title carries prestiege, which can fool some folks into thinking they are really founders. The important part, if you really want to be a cofounder in more than title, is to make sure you have equal share and control with all other cofounders. Otherwise you are indeed just an employee (which can be fine as well if you are satisfied with it).

[hkmurakami]

Doesn't have to be equal. Had to be substantial (depends on stage of joining and how much derisking has been done)

[mathgeek]

To me that's an employee with substantial power, but mostly it's a semantic disctinction which goes to my original point. It does get a little fuzzy when you have enough share to "not get fired".