Calibre is not intended to run on the reader itself, but rather on the computer being used to access the reader. It's only available for Linux, OSX and Windows. Since WebOS seems to be Linux based, it shouldn't be completely impossible to port Calibre to it, however, Calibre needs a rather powerful computer. It will probably not run well on mobile devices with limited computing power.
If the device mounts as an USB removable drive when connected to the computer, it should be possible to get it supported in Calibre as a reading device, though. See
this FAQ entry for information.