Hello, @virbeta, and welcome to MusicBrainz!
You ask interesting questions. It may well be that only a lawyer could give legally rigorous answers, and I am certainly not a lawyer. It may also be that there are no legally rigorous answers except if you specify a jurisdiction (because the interpretation of laws differ from place to place) and maybe except if there has has been a court decision to interpret the particular legal circumstances.
There is a vested interest for lawyers not to answer questions like this, because they might be wrong. There is a vested interest for official representatives of the legal entity for MusicBrainz not to answer, because it is hard/expensive for them to get legal advice about a correct answer, and giving a wrong answer might cause legal risk which an absence of an answer does not. A lot depends whether the publishers of data being copied decide to make an issue of a certain kind of copying. That in turn might be more of a business issue than a legal issue.
I would suggest, however, that it is wise to get comfortable with uncertainty and with shades of grey for questions like this. And, it is wise to avoid assuming that if a data publisher chooses not to make an issue about individuals copying individual data items, that gives assurance that they will also not make an issue if someone writes an automated process to copy lots of data items at once.
As an engineer, I like clear, logical answers. And I like writing code which efficiently automates data aggregation and information creation. But it is a mistake to assume that business issues and legal issues will be clear and logical, even if that is what I prefer.
This is not a clear, logical answer. Sorry. 