It hooks into the games public API to determine items in my price and demand range and does buy orders everyday.
Since it doesn't do any injections, it isn't a violation of the games policies or anti cheats. Been doing it for years.
The items I trade in don't stack in inventory, which makes it tedious for any normal human player. But given the buying and reselling is scripted, it doesn't impact me.
I've generated a few thousand dollars worth of gold over the years doing this.
The games marketplace also is deflationary. 15% buy and sell fees. I imagine I've burned a considerable chunk of gold keeping my operations going.