There are still a few oracle-specific issues left with the content-repository that need to addressed, but enough of it has been ported to support other modules.
The work that remains for the content-repository includes adding a search mechanism, and adding support for xml import/export of content-revsions. In addition, we plan on adding support for storing content in the file-system at some later date.
Before getting started on porting anything that depends on the content-repository, you should familiarize yourself with the "lob-hack" that Don developed for openacs 3.x. The content-repository for openacs 4.x uses either a lob field, a text field or a file (not implemented yet) for storing content.