I guess I'm doing a terrible job of explaining it. Here's what AVT sent me:
That's an interesting question.
Let me tell you a little history about this and in the process I'll
(hopefully) come up with an answer. My memory about the exact order of events and who was involved might be wrong here and there, but the general discussion is correct.
I designed, built, and sold to DHP several models of interfaces. They were OEM boxes, just plain black boxes with my hardware inside. (I still sell that hardware to my industrial customers.) For unknown reasons, the two guys that ran DHP quit buying my stuff and, from my perspective, disappeared.
Then (a few years ago ??), a DHP user contacted me about fixing his interface. He told me that, apparently, DHP had gone out of business (which confirmed what I thought, as they stopped buying hardware from me). He eventually sent me several to repair.
During all of that, he (the user) told me that he figured out a way to program some information into the interface so that the old DHP software would work. He told me how to do it, and I replicated what he had done so that I could fix his hardware. He then told me that if another DHP user bought my hardware I could use the same procedure so that user could then use the hardware with their software. So, I did that for a few folks where I had to repair their interface or, in one case, where they had lost their interface during a move; and maybe a few others.
Plus, as far as I knew, DHP was gone; so I didn't see any harm in it.
I guess someone posted some information about what I could do on a forum (somewhere). Early this year, out of the blue, one of the principle owners of DHP contacts me and tells me that I'm violating his copyright (or some such thing) by bypassing his security features of his software.
He asked (sternly, but politely) that I stop doing that. I thought about it for a while and came to the conclusion that it might be a bit legally foggy as to what I was doing was wrong, but none-the-less, the prudent course of action (and not wanting to burn any bridges, should he want to resume a business relationship) it was best that I agree to stop.
Hence, when someone, such as yourself, writes to buy an interface that is compatible with the old DHP software, I have to figure out a way to say that it 'will' and 'will not' work with that software. It 'will'
because the hardware and software will work, but it 'will not' if the software is expecting the hardware to have some kind of information stored in it - that I don't normally put there (that DHP apparently used to put there).
One more thing. I do not work on cars. I do not have, and have never even seen the DHP software. I have no idea how it works, what it does with a car, and no idea how it handshakes with the hardware.