HexHUD is a mod, as it changes game files for a certain purpose.
I understand textures to be edits of the t00x files.
Really, it could be argued either way. If texture packs start coming out in the dozens like for Minecraft, it might be better to have this here. However, if there start to be large numbers of HUD replacement texture mods in here, they'll probably be moved to Texture Packs so that mods that deal with actual gameplay or content aren't mixed in with interface reskins.
For now, though, there isn't too much in the way of gameplay or content mods as there isn't enough that can be modded yet. For that reason, I see no problem with having this thread in Mod Releases as it is now.
If you want it moved to Texture Packs, Crusade, just let me know. Keep in mind that people looking for replacements for textures, like the HUD, might go to Texture Packs. Otherwise it'll stick around here unless there is a good reason to move it.