Protects against what?
What I read here is just a vague critic from him of the relation between hard- and software developer. Which will not change just because the ISA is open source. It will take some iterations until this is figured out, this is inevevable.
Soft- and hardware developers are experts in their individual fields, there are not many with enough know-how of both fields to be effective.
Linus also points out, that because of ARM before, RISC-V might have a easier time, on the software side, but mistakes will still happen.
IMO, this article doesn't go into enough depths of the RISC-V specific issues, that it warrants RISC-V in the title, it would apply to any up and coming new ISA.
Why would Disney demand that?
Why would they choose slack if they want to host, maintain and be responsible for the internal chat themselves?
They choose slack because they do it for them so that they don't have to do it themselves. That is the selling point for them.
Businesses buy cloud services, because they do not want to manage stuff themselves.