In an earlier technical life I was in the 'Library Automation' biz, where I designed and built library information systems and public online catalogs, and was a VP of Software Development for a major vendor. Central to these systems are bibliographic records - a standard description of a work, such as author, title and subject (which gets more arcane from there.)
The above case was just filed in the Northern District raising antitrust and unfair competition issues.
OCLC is a long standing 'bibliographic utility', who distributes basic 'bib' records and allows member libraries to augment the catalog record according to local needs. They also manage ILL (Inter-Library Loan), a facility through which a librarian can deterimine other libraries that have particular works.
SkyRiver is an upstart alternative utility, affiliated with Innovative Interfaces of Berkeley, a library automation vendor.
In a well-written complaint, the plaintiffs allege that libraries who wish to upload local bibliographic records to OCLC, but not use OCLC for source records, are charged a punitive premium, making the SkyRiver alternative less attractive to them.
Also central to the data infrastructure is a unique number for each bib record - the OCLC number -- which effective brands a record as originating with OCLC.
To understand the impact of OCLC on the library world, consider the role of WestLaw and Key-Cite to the legal world. This case is significant.