What's a co-founder agreement, and when do you need it?
This is a straightforward agreement for two or more individual co-founders to sign at the start of their collaborative efforts.
It's not a standard shareholder agreement. All other shareholders, including any future collaborators to whom you want to extend the title 'co-founder', should sign a different agreement when shares are issued outside of this very initial arrangement.
It's not suitable for collaborations between businesses, which would require a joint venture or commercial collaboration agreement.
If a business and an individual are collaborating, this relationship should be documented with a contract for services, where the individual is engaged by the business.