If you are using Remote Data Access, yes, all users will need a Sage (not Sage 50) login using their own email address and password. However, if you are all in the same location and using a local area network then, no, they don't need the Sage password. On a local area network each  computer needs to be connected with access to the drive and file where the data is stored. This could be on a server or one of the other computers acting like a server for this data set.

Remote Data Access is more for users who are remote from one another and use the internet to connect.

whichever way you are connecting each user needs their own login ID and password for Sage 50. All computers being used to connect to Sage 50 data must have the same current version of Sage 50 installed and the number of users needing to access the data concurrently is limited by the edition of the program: Pro - Single; Premium - 2 or possibly 4; and Quantum is five or more up to 50.