Nirn auction house, and TTC are not however solutions achieved through the API. I believe TTC asked ZOS prior to creating the .exe, but I'm not sure about nirn auction house. Regardless, for both the .exe file doesn't interact with the eso .exe so there isn't an issue with the TOS. But you should still be careful of any .exe files from a security standpoint.Anything that can be made or achieved through the API that ZOS released themselves, is allowed.If they don't approve of an add-on's functionality, they'll generally change the API instead of taking action against the add-on (or its maker). Allowed and safe are two different things, though, and when this particular add-on was first released (halfway through 2017), it triggered all sorts of virus warnings for several people. I've been told that has been fixed and taken care of, but I remain suspicious.