The license defines it: "Making the functionality of the Program or modified version available to third parties as a service includes, without limitation, enabling third parties to interact with the functionality of the Program or modified version remotely through a computer network, offering a service the value of which entirely or primarily derives from the value of the Program or modified version, or offering a service that accomplishes for users the primary purpose of the Program or modified version."

I'm definitely not a lawyer; but as a layman I would interpret that as meaning you can't just change a few cosmetic things in the API to get around these terms, since that clearly still "entirely or primarily derives from the value of the Program or modified version" as well as "accomplishes for users the primary purpose of the Program or modified version".

There's certainly edge cases here which I assume will remain a gray area unless they're eventually worked out in court as part of some lawsuit. But given the intent of the license terms and motivation for adopting it (preventing cloud providers from reselling infrastructure software as a managed service), I would really not expect to see lawsuits against non-cloud providers. I mean there's no logical motivation whatsoever for vendors of SSPL-licensed software to start suing random users who aren't competitors. If they wanted payments from all self-host users, they would have used a very different license.

So my guess is the only way this goes to court is if a cloud provider blatantly violates those SSPL terms, which seems unlikely to happen.