A course in SAS OnDemand for Academics is created and owned by one user account. This account will have read and write access to the course files. All other users invited to the course will have read-only access to the course files. A course cannot be owned by more than one account, so two instructors cannot co-own a set of course files.
The second instructor can access course files in the same manner a student would. Course files can be shared with anyone, instructor or student, by distributing the course code, as described here: https://support.sas.com/content/dam/SAS/support/en/products-solutions/ondemand/EnrollCourse2022.pdf.
Hope this helps!