Is there no distinction for "read-only collaborators"? We build software for many clients, they often request some (say 2 to 10) of their own users be added to

Is there no distinction for "read-only collaborators"? We build software for many clients, they often request some (say 2 to 10) of their own users be added to the repository but only for viewing our work, not committing new code. If they are charged at the same rate as our own users the effective cost per repo for this model becomes $10-$50 per month!