GNU/Linux, commonly shortened as Linux, is an open source operating system.
GNU/Linux is a Unix-like computer operating system which comprises of the necessary programs provided by GNU in Cambridge, Massachusetts and a kernel, developed by Linus Torvalds in Helsinki, Finland.
Most eBook readers use an embedded Linux system. The largest companies in this business are Wind River and MontaVista. MontaVista is the one used on the Sony Reader.