I think that this is useful if you massage it for your own needs. Changing some of the terms and deleting some of the other ones that don't make sense for your business you can create a contract that should work well. I am not a lawyer so I cannot attest to how enforceable this contract is (especially in your country/state) versus one drafted by a lawyer. In California, a verbal contract is enforceable so on the surface this seems like it would be as well.

As an aside, the severability clause is a good one to have in any contract.