From the wiki:
“colLib harvests metadata-records from OAI-PMH-compliant repositories and enables manual ‘tagging’ of these records to cluster them by subject or other meaningful categories. Tags are represented by pages in a wiki, that can be annotated with links to related tags, external links and any other text deemed relevant.”
Here is the page of currently untagged records.
Here are the sources (repositories) from where all these records come from.
So the content is already there, but it is using the collaborative features of a wiki to enable people to apply user defined tags.