The following tech tip (https://kb.4d.com/assetid=4404) tells you how to assign 4D plug-in licenses to specific users. Nevertheless, it does not prevent you from getting a privilege error. This can still happen if all of the conditions below are present:
- A plug-in was assigned to a group that has more users than there are licenses for that plug-in.
- The number of users from that group connected to the database is greater than the number of licenses installed on the Server.

Being a member of the group does not guarantee that you have a license. For example, if 10 users are members of the group that can access 4D Write while you've only installed an expansion pack for 5, the 6th user will still get a privilege error. This is why you should test to see if the current user has a valid license.

The "Is license available" command will return true if the current user has a valid license. For example, the following statement "Is license available (4D Write License)" will return True if you have a license for 4D Write, or False, if not, even if you are member of the group that can access the 4D Write plug-in.

Note: You can also use this command to detect if 4D is running in demonstration mode or if a web license is available.

For more about this command visit: https://www.4d.com/docs/CMU/CMU00714.HTM