Without offending anybody I guess this is cool but what is the ultimate goal? Trimble, JD, and name your company charge fees for unlock codes which sucks because I believe they are excessive. Ipads and tablets are less then $1000 US whereas JD and trimble displays are $5000 + before unlocks. I get the money savings, but If I already have this overpriced stuff I probably wouldn't switch to this kind of setup. ( Not that the BrianTee would care anyway.)
If you have to ask... it's not for you.
I think the goal here is to scratch an itch, fill a personal need, really. Learn how to do cool things. It's fun and very educational. I'm not sure that competition with Trimble, Deere, etc, is really that relevant to this endeavor, though if something became good enough to actually compete, that would be a good thing. I suppose at some point freedom is a part of it; we don't want all the world's knowledge locked up in proprietary systems.
Personally, Brian's project is actually fairly immediately useful to me. I have two outfits I would love to add automatic sectional control to, and in its present state it's almost ready to step in and do this. I already have a SmartBoom on one sprayer, but I payed a lot of money for that and it's now obsolete, unsupported hardware. For a fraction of the price of the Smartboom unit, with Brian's software I can set up a sectional controller for my other sprayer that includes a nice graphics display. So yes this is very useful to some of us.
Do I need a GPS guidance system for my tractor, no not really; GreenStar works well. But I would like an autosteer for my swather. Currently the quote is about $10k. If we could get basic guidance going for a couple of grand that's a win for me.
This isn't the first time you or someone else has questioned the motivation for doing this sort of work. And that always surprises me. I guess I come from a completely different background (academia). Different strokes for different folks. Fortunately farming offers a lot of different kinds of hobbies.