You can restrict other users from accessing a plug-in by using the password system. All you need to do is create a user group that has the only access to a plug-in. You need to log in as the Designer or Administrator to be able to use the password editor.

Here are the steps:
1) While in the 4D Design Environment, click on the Tools menu, and select 'Passwords' to open up the password dialog.
2) Select 'New Group' from the Passwords menu.
4) Type a 'Group Name,' choose the 'Group Owner' and click OK.
5) Drag the names of the users that you allow access to a plug-in to the new group you created.
6) Select 'Plug-Ins Access' from the Passwords menu to open the Access Management dialog.
7) Choose a plug-in in the 'Access to plug-ins' list and then choose your group in the Group Access drop down list and click OK when you are done.

The access to the plug-in you selected is now restricted to the users of the group.