An open set of people—"2 Librarians, A Mathematician, An Economist, a Computer Scientist, a Library developer and a chemist," according to the blog post—has been working on principles for open bibliographic data. They're going to launch it on January 17 at the PMR Symposium.
The four principles expounded in the statement are:
When publishing data make an explicit and robust license statement.
Use a recognized waiver or license that is appropriate for data.
If you want your data to be effectively used and added to by others it should be open as defined by the Open Definition (http://opendefinition.org/) – in particular non-commercial and other restrictive clauses should not be used.
We strongly recommend explicitly placing bibliographic data in the Public Domain via PDDL or CC0.
Some of our own projects have to wrestle with licensing issues, so it will be helpful to have these principles out and officially published. (Hat tip to Peter Suber)