JP1 is not sold, supported, authorised, etc. by
OneForAll or Radio Shack. It is the result of
end users reverse engineering the secret interface
that exists in these remotes to allow factory
upgrades.
You can get info from here:
[Link: hifi-remote.com]including two online vendors that sell the cables
as well as the design and parts list if you want
to make your own cable.
Thank you for the link.