We offer Open Textbook Library MARC records for anyone (or any discovery system) that wants to use them: https://open.umn.edu/opentextbooks/discovery
To your note, Nathan, I just heard from Rose McLendon at Ex Libris who will be ingesting them soon.
As Steel mentioned, these were first created with the team at Colorado State University, particularly Alicia Conrardy, who did a lot of the work by hand. While she continues to advise us, Andy Seroff, a UMN developer, created a system for real-time automatically generated MARC records that we’re using now.
The records aren’t perfect. We’re working on significant cleanup (both in terms of the OTL backend structure and in terms of cleaning up existing records) with additional guidance from OCLC. Our goal is to have OTL records in OCLC in 2020. I believe what’s there now was entered by a community member or volunteer, and I don’t think the collection is up to date.