I think you're mistaken, the Kindle is also Linux based and you can also do anything the cpu/display permits on a jailbroken Kindle. Most people install alternative reader software that supports more formats like epub, but you can do whatever. For a while I used an old Kindle as a "monitor" (connected over ssh) for a server that was otherwise headless. Obviously you can't do anything that moves too fast, but it was nice for doing simple maintenance & system monitoring tasks.