Making users Read-Only on a project is easy!
Step 1: Access to the View/Edit User modal is document in another article here!
Step 2: Once you've found the View/Edit User modal, turning on/off Read-Only access is performed by toggling:
Read-Only Off - User will have normal, standard use and access to all the features and functions of Mastt 
Read-Only On - User will have access to view all of the data in Mastt, but can perform no adding, editing or deleting of data in any part of the system.
Note: If a user is Read-Only On for a Program, they will by default be Read Only for all Projects in that Program!