Before I saw the German, I already had a feeling it was --- I'm not sure why, but I've seen Germans use that style of page a lot (another example: https://www-user.tu-chemnitz.de/~heha/basteln/PC/USB2LPT/ul-... ). That and the encouragement to build one yourself stood out.

This one looks very similar to a 6502, and seems to be much smaller than another semi-famous discrete homebrew computer, http://www.homebrewcpu.com/ --- that one only runs at half the clock speed, but the performance seems comparable.