GRDDL, pronounced “griddle”, is a World Wide Web Consortium recommendation. GRDDL allows one to describe in a standard way how to map information between different XML formats. The acronym stands for “Gleaning Resource Descriptions from Dialects of Languages”, which describes exactly what the standard facilitates.
This is important to Creative Commons because across science, education, and the web there are lots of formats used to describe copyrightable works (and in science, much more than that) and associated rights. These include HTML (and within HTML, data marked up as various microformats and RDFa at least) and dozens of XML-based formats, some well designed, others not so much.
GRDDL makes it easier to process data from diverse formats in an interoperable fashion, when that is appropriate. There’s no requirement to access data via GRDDL, but hopefully the mere opportunity to do so occasionally will make people consider interoperability requirements earlier than they would have otherwise, facilitating lower costs for collaboration across space and time in another way.