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

Don't confuse things. HD only provides minor bug fixes and interface improvements, while BT implies a completely different game dynamic, primarily the absence of morale and global skills, the addition of 3 stacks and 2 levels, secondly, experience potions, etc. The ban on water artifacts, gold instead of scrolls, etc., are all minor things that SOD players could easily accept without any problems, but many will never be able to accept the absence of morale (in BT, this is a sacred canon, however regrettable).