library(bdb) is built on top of Berkeley DB. Berkeley DB
can be downloaded from:
http://www.oracle.com/database/berkeley-db
Berkeley DB for Mac OS X can be installed using MacPorts http://trac.macosforge.org/projects/macports/wiki.
library(bdb) is built using version 4.5.20. It may be possible to
recompile it to work with other versions as well.
When using Berkeley DB under Windows, you should set the PATH environment variable to contain the path to libdb45.dll. Consult the Berkeley DB documentation for further info.