Bookeen doesn't currently conform to GPL not only because they didn't issue full source code, but also because they have to make it known to the user that the application contains GPLed code - for example in the About page - and latest firmware version doesn't do that. So currently Bookeen firmware is illegal in all countries that respect GPL, and using it is just like using pirated software.
When they start conforming to GPL, the Linux kernel and operating system they use on Cybooks will be free, and every user should be able to install it - however, without Bookeen's BooReader application, ie reader and library application, which contain Mobipocket's code, and don't contain any GPLed code, as far as I know (they might contain GPLed code for mp3 player, but I'm not sure about that).
If Bookeen doesn't make it possible to install and use Linux on Cybook without their application, it would mean the application and Linux should be considered a single module, and then the application would have to be released under GPL as well for the firmware to conform to GPL license. (
http://www.gnu.org/licenses/old-lice...ereAggregation)
So in my understanding, some more time will pass before that firmware becomes legal to use.