I’m pretty sure that page dates to before we offered VPS hosting. It’s super out of date.
I’ve updated the page to refer directly to our AUP, which has a more accurate explanation of what is and isn’t permitted. In short, we have no restrictions on persistent processes on VPS or dedicated servers, beyond those restrictions that would apply to any process. (For instance, a script that sent spam emails would be forbidden no matter whether it was persistent or not, and no matter what level of hosting it was on.)