> Does it say GPLv3 on the tin, or does it say "Compatible with GPLv3"?

As per [1], it says GPLv3 on the tin.

  > If you mix BSD and MIT code, the result doesn't suddenly become one or the other, but rather a combination of both, right?

The two pieces of code retain their original license, but you can distribute the combined work under just BSD.

[1] https://interoperable-europe.ec.europa.eu/collection/eupl/li...