I have seen the term embedded linux, which I understand to mean any device where linux is "embedded", and the enduser of that device only interacts with it via the application that runs on the embedded linux.

What about the situation with an open platform like compactPCI or advancedTCA? Here you have a platform where you may have Linux running on one or more processors in the platform. The enduser is still really only concerned with the application, but they do have access to the Linux OS for things like application software upgrades, backups, etc.

Is this latter case considered "embedded" linux?

what do you want it to mean?

how long's a piece of string?

Embedded, as I understand it, is when an OS is "embedded" in the hardware, on FlashROM or something similar.