We solve this by placing the library in a folder with the appropriate read only access. The problem comes when someone with read write access has it open, then no one else can open it. So we have a copy of the library in a limited access read/write folder which is copied nightly into a read only folder that users can access. This protects the library, allows multiple users to open it simultaneously for use, and has a write version that can simulaneously be open for editing. A more elegant solution a la - “the library is open by another user, would you like to open it in read only mode” would be useful.