Best Answer: A user CAL limits the number of people who can operate a program; a device CAL limits the number of computers that can run a program. In the industry, user CALs are often called seats and device CALs, cpus.. For example, suppose you have a client-server customer billing program for a large company. If the program sells user CALs, then it basically says, you must pay for each and every customer support person who uses this program..