Maarten Sneep has created a pdflatex macro for embedding XMP in PDF files generated from LaTeX source, the de facto standard for scientific documents. As Maarten’s documentation points out, one may obtain XMP suitable for embedding via choose license process.
We have a tech challenge calling for Creative Commons and XMP support in open source applications. Follow Maarten’s lead!
Update: The software above is available via CTAN: the Comprehensive TeX Archive Network. The package is called xmpincl (the second link in this post points to a CTAN mirror). Also of note, xmpincl is licensed under the CC-GNU GPL.