> to just copy all of Ubuntu's (or Debian's) binary packages and build a new derivative distribution on top of it
This is okay. However, copying Ubuntu’s and Debian’s packages into the same repository and then mixing them willy-nilly is not.
You can either:
a) Base your derivative on binaries from Debian xor Ubuntu, then add source packages compiled with these binaries as you like.
or
b) Base your derivative on sources from Debian and/or Ubuntu, then compile everything together with your custom packages to make sure that all ABIs match.
Pack boxes of 50% books and 50% clothing/computer parts/bedding/everything else to make the boxes lighter and get a good indication when you have enough books (i.e. when they really do make up 50% of the content of your boxes).
I’m not part of the age group yet where people would be able to afford books only to look good to their peers. And while you are certainly right that public libraries might make it possible to read many books without owning any, I found that most people who like books use them to read more books, but still get the usual 5-10 books per birthday/christmas/you-name-it to fill their bookshelves.
Of course it is a heuristic and there are both false negatives and positives, so YMMV.
And, conversely, up until ebooks existed, walking into a flat without any books was a clear indicator that I’d be rather bored by the person living there.
This is okay. However, copying Ubuntu’s and Debian’s packages into the same repository and then mixing them willy-nilly is not.
You can either:
a) Base your derivative on binaries from Debian xor Ubuntu, then add source packages compiled with these binaries as you like.
or
b) Base your derivative on sources from Debian and/or Ubuntu, then compile everything together with your custom packages to make sure that all ABIs match.