This article is from a FAQ concerning SCO operating systems. While some of the information may be applicable to any OS, or any Unix or Linux OS, it may be specific to SCO Xenix, Open There is lots of Linux, Mac OS X and general Unix info elsewhere on this site: Search this site is the best way to find anything.
As a general rule, if someone is logging in, that consumes a license, where a service usage does not.
It gets a little confusing though: an ftp login or a pop mail transaction do not consume license.
See Which networking utilities consume user licenses in SCO OpenServer and Unixware? for the gory details.
On current versions, "brand -u" tells you how many user license are currently in use. It will return a negative number if that number exceeds the licenses you have purchased (the license manager lets you "cheat" a little bit pre-5.0.7).
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