By default, ProtoShare for Google Drive designs are only viewable and editable by you. Like any other Google Drive document, you can share your designs with other users.
When you share a design, you have the option of allowing read/write access or read-only. Users with read-only access will be able to view the shared design, but without the editor interface.
If multiple users have a design open and changes are saved, a warning will be displayed to all other users warning of this.