The main reason to become a foundation is to have some legal entity to deal with money. Some times projects get grants or donations or google summer of code men

The main reason to become a foundation is to have some legal entity to deal with money. Some times projects get grants or donations or google summer of code mentor payments, and that can either go into a random account of whoever happened to be in contact with the donor, or it can be properly managed by a foundation with agreed-upon guidelines on where to store money and what it can be used on.