In my head OpenERP was the company that took contributed code, changed the license and slapped a price tag on it? (Anyone: Feel free to defend them, - it might just be my bias against AGPL and the fact that I thought their price tag for the commercial version was unrealistic last time I evaluated it.)
Of course, Odoo has dependencies on several libs but the whole code (framework and the 240 official modules) have been written from scratch. (I wrote a huge part of it)
That's actually the reason why it's so integrated; there are no interfaces between the different apps; every app is fully standalone (you can install project management only) but fully integrates with the others when you install more modules. (timesheets on tasks, billing of projects, contracts related to projects, ...)