Is there a DIY alternative?
The schematic is available in the How It Works page. A made in USA quality bareboard is available. A parts list of the components needed to assemble the board will be provided with the board. The parts are available from Digi-Key or Mouser. For the advanced hobbiest the parts placement is obvious from the boards silk screen, reference designators, and a close up picture of the board.

For DIY, do I have to use the case in the reference design shown on the site?
The case used in the reference design has internal extruded slots that the board slides into eliminating mounting hardware. The board does however have holes for mounting the board on standoffs in a custom configuration.

Which wall adapter do I need?
It uses the popular wall adaptors that are typically used with BOSS style jacks. You want to use the musicians standard pin configuration and not the electronics industry standard. In other words, the barrel is POSITIVE, NOT NEGATIVE. And the pin is NEGATIVE, NOT POSITIVE. The AS-3 is protected from reverse polarity if you do try to use the wrong one.

Does it use True ByPass?
True Bypass is a term which simply means the input signal is switched to the output jack using simple mechanical contact closures, whether via an actual mechanical switch or via relay contacts. For the typical ABC selector this would be the default method since they only consist of simple mechanical contacts. True Bypass makes a lot of sense for an electronic device like an effects pedal that may load down the instrument pickup or transducer when it is inactive. The AS-3 is not an effects pedal. It is active the whole time it is being used. When it is not being used it doesn't need bypass since the instruments are not being used either.