That's why I'm asking -- if building from source doesn't really change anything why then even consider a difference between sources and binaries in software licenses?
Copyright law is activated by the action of distribution -- you make something, you share it, copyright law checks whether you had permission to share it.
It's legal for someone to distribute you code under one license, and someone else to separately distribute you code under a different license -- it has to be. Once you combine them on your machine, you've created something that would no longer be legal were you to distribute it. But you don't plan to distribute it, and as long as you don't do so, you haven't violated any copyright licenses, because you didn't engage in any acts of distribution for copyright law to have power over.
But the distribution is on you, not the person who gave you the source. The thing they distributed wasn't violating any licenses.
I understand the reasoning, but I don't understand how the lines are drawn here (or how they could meaningfully be drawn).
Distributing two pieces of source code with different licenses is ok. Distributing them in a way that they can trivially be combined (e.g by compiling automatically on the receiving end during installation of the latest Ubuntu) can't be considered different from a distribution where the receiver takes more manual steps to combine them.
I'm curious why Canonical have to use binaries if they could easily just produce them on the clients machine and thereby not violate any copyrights? There has to be something else to it (or they just want to test the limits of the license conflict here, as a useful experiment).
