I'll write it in my will to have the NBB source released.
I wouldn't get your hopes up for a whole lot of comments in it tho.
right now I am working on V2 of the NBB SDK which allows 3rd parties to make just as feature rich modules as I have made for it. It includes all my subclasses for dynamic color changing and all that other good stuff. The biggest problem is writing the documentation. I can give you the SDK now but no programmer will be able to use it without directions.
I think you are getting close to finding an approach that will get you what you want tho. I myself am not willing to start all over on a brand new FE, I have put too much into NBB, and it is obviously important to me. I also don't feel like releasing my source for the core application. However, what I would do is accept a bounty to create an open source module or two for NBB. the biggest thing holding me back from developing OBD2 and GPS/nav modules is the lack of hardware I have. I have no carputer I have no GPS module I have no OBD2-to-serial-to-USB capability. If somebody donated money or hardware those things would get done sooner rather than later. that is why I am working on an XM radio module for NBB; I have no interest in XM radio myself, but somebody who did sent me the hardware and now I have successfully interfaced with it and have only to write a module. the hard work on that end is done it is just time that I am finding hard to come by.
just remember I am only one person and can only do one thing at a time, and most of the time that is my actual job that puts food in my mouth. Give me the hardware/money and point me to some documentation on the subject and I'll get you what you want. its just a matter of time.
Navigation solutions (especially good ones) are very complex.
what i suggest (assuming an NBB module solution) is somebody grab the mac compatible guts out of the best open source mac or unix compatible navigation program and bundle it into an open source navigation module. I will even help