Quote Originally Posted by Packetdancer View Post
I mean, this is getting a little ridiculous.

But treating the question seriously...? No, it doesn't count as third-party software.

In the sense it's used in the ToS, third party software almost certainly refers specifically to software which either alters the game process from the intended state (mods, in-game overlays, etc.), alters the game data from the intended state (mods that directly affect the game assets on disk), or extracts information not accessible by any other means.

Moreover -- and this is the key point -- any software the game cannot function without is not unauthorized third-party software, but rather part of the game's base operating requirements.

Windows, in contrast, is the host platform on which the software is designed to run; the Windows version of the game cannot function at all without Windows. (Or some sort of reasonably complete Windows-esque API translation layer, a'la WINE, Proton, Crossover and such.)
If you want to get real technical and nit picky about what their vague definition of third party software means then...

Discord can count by this definition as you can toggle an overlay which appears in game. It's just a list of people who are speaking in the voice channel, but an overlay is an overlay.

ACT Parsing would not count by this definition (with just base functionality installed) as it does not alter the games data and does not alter game assets. It reads network data and computes that into a parse.