Probably because Jackson figured 99.99999999% of guitar players aren't interested, and they let the patent expire (the JE1000
was introduced over 20 years ago).
I built a JE1000 from scratch about a year ago. I was originally going to mass-produce and sell them, but my prototype had a flaw in the circuit layout. While I did manage to complete one fully functional unit via some messy soldering, I decided to scrap the project for a few different reasons:
1. It's very time consuming.
2. It looks like crap. (even though it works perfectly)
3. It's probably illegal to sell them, especially with my Johnson'd Jackson logo.
I have the schematic somewhere, but I can't seem to find it at the moment. I got it from the jacksonguitarpalace forum, although it seems to have been removed.
My advice would be to just buy the EMG ABQ, as it appears to be the same as the JE1000 (except with surface mounted design components). The sound should be identical.
I have 3 uncut boards like this: