HoMM3 HD is a mod (add-on) for the game Heroes of Might and Magic 3.

I didn't know that HD-MOD also works in HotA.

I am one of the developers of HotA. HotA is developed according to the same principles and on the same platform as HD 3.x, so it is the only fan-made add-on that is 100% compatible with HD 3.x, just like SoD.
Currently, I am not actively involved in the development of HotA, but I participated productively in the past and now I follow the work. The main and currently the only programmer in HotA is Sav; if you follow the HD changelog, you can see that
it includes Sav's work on fixing SoD bugs.
In general, I believe that the future of tournament games lies with HotA, because
serious work is being done on the map generator and balancing of cities, but without any WoG-like features. And in terms of fixing bugs in the original game, the future HotA 1.3 is ahead of HD. In combination with the features of HD, HotA should be very attractive for Heroes fans.
Here is a small advertisement from me.