// Is this any good? //
You make it sound like this is some kind of 'home-brewed' agreement. Since you are asking an internet forum, I take it none of the partners can afford genuine legal advice, at this stage? How will you know whether any of it is going to be legally enforceable?
My personal opinion is that contracts are for when a group of - otherwise equal - people cannot trust one another to only take their fair share of something worth having or where there is no inherent cause to trust the other party to perform their share of the bargain, such as the employer/employee relationship.
For instance, the work could be divided up by the project leader in such a way that, even if you arranged for 100% intellectual property rights on the pieces code you write, none of it performs useful functions until it is integrated with the code your business partner(s) write. So you won't be able to sneak away and make a fortune with solely the pieces you built. ;-)
I have not seen movie 'The Social Network' but I gather the plot revolves around a "gentleman's agreement" gone wrong, or a contract that was too sloppily written - because they were skint students and couldn't afford to get a proper lawyer to write it.