Not a surprise. I have been a fan since 2014 and the game was in development since before that even! Here is a simple explanation, in order:
1-Harem V0.6b.8 that I just uploaded (because it had disappeared off the internet) was the final release of the first, Original, Harem Game that
ker made.
2-Harem c8m7 was the final release of Ker's First remake of the game. This is the version that progressed the furthest, as well as the final version that Ker worked alone on.
3-Harem C5.0 is an unofficial remake that Ker wasn't involved in at all. The developer did some quality work though.
4-Harem Remastered (current version c4m5) is the current version of Harem. Ker was involved in the beginning and has given his blessings to the team to carry on.
And as a bonus there is "Harem Experimental" that I just uploaded after it too had disappeared off the internet. It is made by Ker and is basically a small experiment: a bunch of Harem's scenes remade in a more realistic art style.