[Question] WoW 3rd party Overlay Apps

So I’d say I’m relatively new to the WoW scene, since I started in shadowlands. I was very surprised to see so that addons have so much access to the game. So naturally, I was curious if there were overlays. I will admit I did not look very hard for overlays and my results were basically none.

Although, I did find a thread regarding the usage of warcraft logs which in fairness seemed pretty broken and should not be allowed.

So what I’m curious about is, How come there isn’t any overlay apps developed? Is it purely because addons are all contained in 1 space? is it because overlays are against TOS? If its the latter, why would addons like TSM or Auctionator be allowed as addons but not as an 3rd party overlay app?

I don’t know what you mean by an overlay app for WoW. I know Discord can overlay who is in a voice chat channel onto anything. But what exactly is an overlay specifically for WoW?

I play Path of Exile as well and in that game there are some overlay apps where its job is act as a tool to improve your QoL in game. For example, one of them is a price checker which uses the game’s API to help players price check an item before selling it without having to actually go to the game’s trade site to check.

Or another one that assists players by tracking how many pieces of equipment they’ve picked up that qualify for this vendor recipe. But this updates only when the player has gone through a loading screen.