Earlier quoted context omitted.
This is why open source is rapidly becoming obsolete ;) There have been source-available/fair source/whatever-you-name-it approaches before. They were attacked by OSI zealots every time because it's not real open source. Which is true, but the unsaid - or well, only sometimes mentioned - other half is that these open source enthusiasts would you rather have a bog standard all-rights-reserved commercial licence than a…
The freedom to host open-source software is more important than contributing back to the original project: it's where the actual value of open source comes from. Would you host your website behind Apache or Nginx if you couldn't just switch providers and keep the same web server? Would you ever pick up Postgres or MySQL if you couldn't actually pay a company to host that for you, knowing that if they screwed up, you…
Let's not get everything mixed up here - I singled out BUSL exactly because it does not prevent competing services, especially at small scale. In fact it would encourage small business and individual usage vs big cloud providers. It also has a conversion clause, so worst case scenario you have a slightly outdated MIT-licensed release to pick up from.
The EUPL the author mentions, the AGPL and others are the ones that directly prevent competing services.
That said, indeed it might not be an ideal choice for that kind of cloud-hosted software if you want to maximize adoption.