This one is the original HHS 1 made by Pookla.
Then came atztek1 and wanted to make his own version (a spiritual successor, not an actual copy) in the VB.NET framework and did so with Pookla's permission. That was HHS 2.
And at some point atztek1 stopped working on HHS 2 and started HHS+ (which is basically HHS 3), which is in many regards exactly the same as HHS 2 but with some additional features like connected locations, visible NPC paperdolls, interactive buttons and a rudimentary built-in event editor. (I believe all events in HHS 2 were hardcoded into the game.)
Eventually I and others got interested in that editor and started contributing some events. But since I found the editor lacking for some of the things I wanted to do and with way too much overhead in other aspects, I also joined the project on the code front and created a completely new editor from scratch, where events consist of individual building blocks. Of course, all events were still very much like in HHS 2, since they originally got ported over to the classic event editor and then to the new one. And some images from those events have been around in HHS 1 as well.