"Pogoplug Software enhances your personal cloud experience by letting you stream files, photos, music and movies stored on your computer(s) to any connected device, anywhere. Our new also software includes OneView™ of the files and media stored across all your computers (and hard drives, if you have a Pogoplug device) from one friendly interface."
"I also wanted to let you know that our new Pogoplug Software comes in two flavors, including a free version. Use the free version to remotely access all the files stored across all your computers, and upgrade to Pogoplug Premium to stream your media."
Since they are opening up their "cloud" service for non-pogoplug devices and offering a free version it might be possible to squeeze them for access to their API or even to now finally open source part of the service shipping with the plugs themselves.
Apparently they ARE offering a Linux version though the source will probably remain closed forever and only offered in x86 flavor:
Operating Systems: Microsoft® Windows XP/Vista/7, Apple® Mac OS® X 10.6 or above, Linux