I wish that too. More than that, I keep wondering whether there could be a way to force companies to interop, because right now you generally can't, without getting into some sort of business relationship with these companies. That's the problem with services - they take control of interop, and the extent to which interop is allowed is controlled by contracts between service providers.

Where in the terms of service does it say that third party clients are disallowed?

(It doesn’t.)

While it does not explicitly state that, it does say:

"(ii) copy, adapt, modify, prepare derivative works based upon, distribute, license, sell, transfer, publicly display, publicly perform, transmit, stream, broadcast, attempt to discover any source code, reverse engineer, decompile, disassemble, or otherwise exploit the Service or any portion of the Service, except as expressly permitted in these Terms;" [1]

Given that the API is not public if you are not using a bot key, I would think that using it with a third party client would take some form of reverse engineering.

The devs also stated that other client modifications like betterDiscord are against the TOS.

[1]https://discord.com/terms (Under Right To Use The Service)

Ripcord isn't a modification of their software. It's an original implementation. I didn't look at any of their code.