It seems to me like mostly wishful thinking, or at least I have never seen these two points actually written in a license, let alone implemented in practice:

- the seller guarantees the software will work as documented, won’t be infected with malware, won’t be riddled with security holes, won’t contain plagiarized code

- the seller provides support and maintenance via e-mail, with a response-time service-level agreement

Usually there is a clause that is the exact opposite of the first (i.e. no obligation that the software actually works for what it should), and the second in practice means "if you e-mail us, we will open a ticket with no deadline whatsoever, we will solve the issue or completely fail to in whatever time we see fit".

Admittedly, I have not a lot of experience with commercial programs that offer a service of assistance, and generally speaking they do work just fine (and contain no bugs/malware/etc.) but the few times I found something not working as expected (actually as it should) it was a nightmare to have the issue fixed in a timely manner (or at all).