Can someone please explain, in depth, what exactly this is and why I'm being forced to move to it instead of my beloved FuBar?

http://wiki.github.com/tekkub/libdatabroker-1-1/home

This move is a good one and is following current trends in the programming / computer science field. It's all about separation of data from display. In the long run this will make for cleaner, more stable, and portable plugins that can be used in not just FuBar but whatever you want without the need to recode the addon. You can and will see FuBar plugins around for a long time so there is no forced move yet :)