I not entirely sure but from what I can remember Andreas Kling is seen using Mac-os in a Ladybird update video so it could be possible that it is his main operating system. Take this with a grain of salt.

What was the original domain?

The reason for why I think it said usually considered transparent is because when you have a less busy track it sounds transparent and I think its from the perspective of the average end user.

Do you have any exact statements from them? Because I would like to know more.

I rarely hear about authors/artists talk about copyright other than, when they talk about what license they use or them complaining because they felt that their work wasn't infringing on other artists copyright since it was transformative.

How long do you think copyright should be? It was originally 14 years in the United States.

The length of copyright protection depends on several factors. Generally, for most works created after 1978, protection lasts for the life of the author plus 70 years. For anonymous works, pseudonymous works, or works made for hire, the copyright term is 95 years from the year of first publication or 120 years from creation, whichever comes first.

https://www.copyright.gov/history/copyright-exhibit/lifecycle/

The max that I would ever be happy with is 25, but 20 or 17 preferred for me at least. I think it gives plenty of time for a Series completion.