Originally Posted by igorsk
Actually, GPL does not "require" to release the source code. However, it's one of the options you have when using GPL software. Two other options are to stop distributing your product or to replace the GPL code by non-GPL equivalent.
It's not exactly "releasing" the source code what the GPL asks for. What you should do is give the source to anyone you give the binaries to at no additional charge, and if they ask for it. That is, they wouldn't need to release the source code publicly, but it should be available to any legal owner of a Cybook. And of course, it would still be GPL, so the owners who get the source code can freely distribute it if they want, but that's a different story. From the seller's point of view it is: I sell you a device with GPL software, if you want the source code of the software, just ask for it and I'll send it to you or tell you how to get it.