3rd party software
Auto-Clickers aren’t allowed, as it’s multiple-actions using one keystroke. I’m not sure what the other does, but it sounds like it might be against ToS as well.
There’s a sticky on the main forum page:
https://forum-en.gw2archive.eu/forum/game/gw2/Policy-3rd-Party-Programs-Multi-Boxing-Macros
Safest bet is simply don’t use them, to be honest. There are a few grey areas regarding some of them.
The only third party app I know of that is specifically allowed by ArenaNet is Overwolf.
I’ve never used it though.
http://wiki.guildwars2.com/wiki/Overwolf
From searching around, GW2 Helper looks like it’s just an overlay app, putting various info on screen about the game that you normally wouldn’t see (such as the exact amount of hit points an enemy has, displayed as a number on their health bar). It doesn’t seem to have any hack or bot type features from what I can tell.
I have seen other players say ArenaNet is OK with overlay apps as long as it doesn’t give an advantage or automate gameplay. I’m not sure about it though.