Like other cals cal suites can be licensed on either a per user or per device basis.
Windows server cal user vs device.
A client access license cal is not a type of software but rather a license that grants users or devices access to sql server software.
When you use the per device model a temporary license is issued the first time a device connects to the rd session host.
A cal gives users or devices the right to access and use services provided by a windows server.
User cals are the more common licensing option.
Sql cals are a requirement only for the sql license cal model meaning that if you purchase sql server licenses per core standard core enterprise core you will not need to purchase any additional licenses.
With the user cal you purchase a cal for every user who accesses the server to use services such as file storage or printing regardless of the number of devices they use for that access.
Device cals allow access to all instances of a particular server product from a single device a laptop or a desktop computer for example regardless of how many people use that device.
Windows server cals do not come with a product key as windows server operating system licenses do and do not need to be registered anywhere in the os.
Cal suites simplify licensing and tracking by reducing the number of licenses that are necessary to access microsoft servers.
A client access license cal suite is a single license that provides use rights that are equivalent to multiple licenses.
Device cals are less common that user cals but they do make sense when multiple employees use the same computer.
Each user or device accessing a licensed windows server requires a windows server cal or a windows server and a remote desktop services rds cal.
The second time that device connects as long as the license server is activated and there are available rds cals the license server issues a permanent rds per device cal.
Even though user cals are more expensive buying one cal will be much cheaper than buying four.