Oh dear, I've followed RE1.5 stuff for years, but fell off after the Magic Door build came about.
What happened that someone ruined our chances of 1.5 being leaked?
What lead to the Magic Zombie Door build getting released actually fucked things over behind the scenes for Team IGAS. They were in contact with someone who owned the final build of Resident Evil 1.5 (whether it was 65% or 80% done was a debate that was had on The Horror is Alive, rest its soul) as far as I understand it. From the research I've done, that's up to the very final boss of the game inside the train much like in the final version of RE2, albeit this is the prototype Birkin we're talking about (I think it was Inflames or some old Resident Evil fansite that got a bunch of blurry, mid-2000's phone camera grade photos of someone who owned this build of the game in Japan as I understood it. It has stuff like a playable Marvin in the factory office with a bite wound that's bandaged up around his foot and a few other things not seen in the current build)
Anyways, what happened was that a user named Colvin apparently knew someone at Team IGAS, and was buddy buddy with them enough for the team member to apparently make a copy of the version of Resident Evil 1.5 that they had personally. This was the 40% build that I forget who it was that got a hold of it off of an eBay sale on THIA, but they were a regular poster there. The dude then posted it out for all to see, as there were skeptics who weren't sure what build of the game the MZD was based off of. This build in particular is what Team IGAS was basing a lot of their work off of. It's mostly in Japanese, with a lot more broken stuff than what's in the MZD.
Naturally, the member of the team wasn't supposed to potentially let the secret out that he and the rest of Team IGAS (outside of MrBZork and that DrBirkin or whatever the other guy who chimed in occasionally at times on THIA, I don't know how big the team was) had their hands on this build of the game, let alone that they were trying to recreate the original version of Resident Evil 2 with help from someone who, in the event he sensed something was off, would cut off contact if it came to it. Well, when Colvin tried to sell his disc on eBay, that's when shit hit the fan. Team IGAS, and I think maybe some members of THIA (read: anyone who was a moderator or a longtime poster on the forum) who had been looking for anything that would lead them to get the build of RE1.5 were scrambling, trying to contact I think it was eBay staff and/or Facebook to get the sale taken down, and they eventually did so, but to protect themselves, I think they ended up releasing the the MZD build, which was a build that was compiled at an earlier point in their workflow compared to some of the progress they had displayed in some of the videos on MrBZork's channel.
I know these are some big blocks of texts that tended to ramble on and mention this and that here or there, but even I don't remember the minutae of how it all went down, as I was told by others. Unfortunately, The Horror is Alive forums where a lot of the discussion for Resident Evil 1.5, let alone the Cool 1.5 Screenshots thread has been down for quite a few weeks, with the site's maintenance being all over the place.
I will say that Team IGAS eventually contacted Gemini (PS1 hacker who put together the translation patches for Persona 2 Innocent Sin and one of the translation patches for the PS1 version of Tales of Phantasia, at least) who developed this Resident Evil-esque engine called Squeeze Bomb for PC, and that's where the majority of the work is supposedly being done atm. That's the last update we ever heard from him on the matter on THIA. Nothing specific has been states since. I saw on a reply to one of the man's videos (if you look up Loboto_3, you can find his Twitter account, and probably links to his YT page from there) that the work required on this game would take about as long as AM2R. All the while, he's been releasing mods for the PC versions of the classic versions of the RE trilogy and the first Dino Crisis that make the games more compatible with modern PCs, but nothing has been said of Resident Evil 1.5. Chances are, they are probably taking an AM2R approach in regards to releasing the game; make sure everything's done, release it once, let Capcom send a virtual Hunter to DMCA the original link, and let what goes on the Internet, stay on the Internet.
I was following all of this at one point, but nowadays, it's kind of more like how it was with AM2R until I just so happened to check DoctorM64's blog and discover that the game is actually almost done, like, one month from the fact. If it happens, it happens. If not, I think what Kamiya-san and various people have said about the game probably holds up now that everyone's looked at the game and seen at least partially what's in it. I know that's passing judgement on a game that we don't have the final build of, but I think the Resident Evil 2 we got, all things considered, is the better product by far, even if the factory section of Resident Evil 1.5 does have me wondering what could have been.