Mlem is licensed under the Commons Clause, which prohibits commercial use, even though the project advertises itself as “open source”.
The maintainers have refused to accept PRs that change the wording to “source-available”, edited comments and locked threads about the topic:
It anyway doesn’t claim license is not “open source”, just not free. That is very different. Source is open, cannot be freely utilized
That is correct. I’m OK with them using “open source” as it’s valid.