Licence freedoms don't have to be all or nothing, or apply to everyone in the world. It can be open source and have restrictions. Anything else turns open source into a religion.
See Llama's license: if it can be Open Source while having restrictions, then having an Acceptable Use Policy is okay, right? So Redis could create a license that bans its use if you host adult content, Star Wars fan fiction, or documents containing the letter R?
If Open Source doesn't mean a license that indiscriminately grants a set of specific freedoms then it's pretty useless as a term—all I know on hearing it is that a project's source code is available. Which reminds me, we already have a term for that: Source Available.
Open source means exactly what people say it means and what they want to understand by it
However I think Postgres is a bit different. It's a bigger market and more widely used. There's a need for tuning services no matter which platform provides the database servers, so there's a level to make money above cloud hosting.