Have each user follow the steps for adding a subscriber, thus making them the project provider.
Step 1: Log into cloud.measuresquare.com and click on the projects tab.
Step 2: Click on the share icon at the top right.
Step 3: Select from the options to Share All Projects OR Share New Projects.
Step 4: Enter the Subscribers email address. Then select Can Edit YES or NO
Step 5: Click Send email.
You can verify the Provider/ Subscriber from the Settings Tab.
Related Links:
Managing and categorizing your group members
How can I share my diagram through the Cloud?
Viewing and editing your M2 ID information