Ethan is a really nice guy. He would probably be happy to discuss it with you. I have lost track of him, you will have to do some searching to find him and ask.
[EDIT]
(Some more details as I remember them)The Golden Gate Bus card was originally developed by someone else, I can't recall his name. Ethan Dicks bought or acquired the rights to produce the card and develop the drivers for it.
[EDIT #2] I seem to recall some of the discussion about the card and drivers took place in Usenet about 8-10 years ago. I probably would have been comp.sys.amiga.? You might try searching Google for information. The web page still seems to be up here (note the mention about the crash of the development machine at the bottom of the page:-)
http://penguincentral.com/GG2/
About the Beta 2.0 IDE driver mentioned on the site. It was developed around the stock Seagate ST3144 120 meg IDE drive that came in the A4000D. Although it was working with that drive, he (Ethan) was having problems getting larger drives to work. I was testing for him at the time. It was in the middle of this that the A4000 he was working on went down.
-Jeff
@Zetr0 Could you please share information in detail about the soldering/desoldering equipment that you are using? It is time to update my equipment and it sounds like yours is working well.