I don’t see any reason that fair use limits or blocking interactions that behave like attacks should be incompatible with allowing and not penalising the use of third party clients.

Let’s not be ridiculous. DOS is not use, it’s abuse.

I want to preface this with that I agree with your point that DOS is abuse and not actually trying to use the platform.

I disagree with calling the question ridiculous. If we’re involving legality like the poster up thread implied with making this illegal then there needs to be some sort of test or rule put in place on what constitutes illegal activity. We currently don’t have one and whenever a new rule is put in place you quickly find out that there is a significant chunk of people who would find anything you think is obviously wrong to be obviously right and vice versa

And using their servers and resources without generating them any revenue is not abuse? They clearly don’t want you to run a third party app without ads, yet you feel entitled to it?

No, it's not. In this case, abuse is about intent: DOS intends to cause distress, losses and denial of service to others. Use with third party apps without adds intends none of this: the intent is to use something else to access the service in an otherwise normal (to the user) way.

Arguably third-party apps that are scrapers are somewhere in between these two in acceptability, but that's a question of "are scrapers morally fine and should they be legally allowed", not a question of whether third party clients are to be allowed at all.

If I access your API I’m using your server because you offer it publicly. That is not abuse.

The distinction is about whether you should be able to offer something publicly, taking advantage of public infrastructure to do so, and then make demands about what the public do with that.

Companies want to do the electronic equivalent of putting copyrighted media on a billboard in a public square then claiming you need to sign a contract to look at it and then only through special glasses they provide.

When you signed up for an account you agreed to those terms, the api is not public/unauthenticated.