As I understand it the Karma runs ecos, which is a GPL embedded OS from RedHat. So I guess that means that the source of the ecos kernel used by the Karma will be available to those who want it.

The version of Ecos we use is old enough to be under the old Red Hat Ecos Public Licence (RHEPL) rather than the GPL -- but the upshot is the same: yes, the kernel source will be available.

Does this mean that the Karma will be "hackable" or is the hardware protected to stop people running their own code on it ?

The hardware is protected. (Not that hacking stuff would be easy if it weren't: like most embedded "kernels", Ecos links statically with "userland" into one monolithic binary. Picking it out and patching in a new one is not the same thing at all as simply reflashing a zImage somewhere.)

Peter