or is there some streamlined DIY option that doesn't involve knowing anything about programming a "Teensy" (whatever that is). I can solder well enough that I don't mind messing with that, but I have way too much going on right now to attempt learning anything about keyboard signaling and protocols and such. I'd be happy to purchase a sort of "Kit" with a diagram that tells me to attach a to b, but if it involves research and digging through 30 pages of thread and mod logs, I'd just as soon buy the prefab thing. I don't wanna spend more brain effort other than lining up what goes where.
I think he made it clear in the OP. He doesn't want to spend brain effort reading the documentation or the thread (not surprisingly! There's a lot of information there, I would be daunted myself). Soarer's code does require thinking to lead, as evidenced by the number of people who make mistakes loading it, or otherwise can't figure it out. There is no "streamlined" diy solution.
Compare to the world of DIY audio. There, I can buy a kit, solder it up, plug it in, and be done. Lots of fun, no wasted brainpower, etc. In this case, more thinking is required. You have to look at the thread, figure out which board pinout is yours, make sure you wire it up correctly (don't mess it up or you'll forever damage the board beyond repair!) doublecheck your work, get soarer's code loaded, etc. It requires doing your homework, etc. It's not for everyone.
DIY isn't for everyone. Something that's easy for you may be very difficult for someone else. That's why there exists (and must exist) other solutions. The hagstrom is expensive, but known to work and also turnkey: no setup required. That's why I recommended it in this case.