Software licensing can soak up a large chunk of the average organisation's budget, so it makes sense to investigate whether costs can be reduced by being clever about licensing so that you have to purchase less licences for one or more of the products you use. The theory is simple: if the total number of people who use a particular application (call this X) exceeds the maximum number of people who ever use it at the same time (call this Y), there's the potential to limit your licence purchase to Y copies, not X.
If you're going to implement concurrent usage licensing, you'll need some way of monitoring the usage of the applications. There are plenty of packages on the market that will help you out (see end of article for a listing).
The thinking behind concurrent licence management is simple: when a user runs an application, this fact is logged with a central server so that it can keep track of how many copies are in use. To be strictly legal you can tell the system to prohibit further copies of a program to be launched once the licence limit is reached, or you can take the alternative approach of not enforcing the limit but simply purchasing extra copies should you see that usage exceeds the number of licences. The latter approach is less disruptive, but although you're unlikely to be prosecuted so long as you purchase extra copies promptly, you are breaking the law until the purchase is made.
Some applications are based on concurrent usage anyway, and have their own mechanisms for logging the number of copies in use. There's usually no problem running your own system alongside this type of proprietary offering.
Although most desktop software, and a great deal of server software, base their licences on per-user restrictions, many packages have options that throw away the user limit completely. Microsoft SQL Server, for instance, can be licensed per client connection in small installations, but for larger systems you can buy a per-CPU licence, which has no fixed limit at all for concurrent usage. Other products are available in site or enterprise-wide licences.
It's important to examine the options available when you're buying your software, as you may find that there's a sensibly priced "unlimited users" option that has a lower TCO than implementing a licence manager with a user-limited licence. And if the price list doesn't mention an unlimited option, don't be shy to ask the vendor the fact that it's not mentioned on the list may just mean that they didn't know anyone might want one.
The main caveat with concurrent licensing, though, is the individual software licences themselves. Just because you have a way of monitoring concurrent usage doesn't mean that it's necessarily legal to use it with all the software you run.
Imagine you have package A running on 200 desktop computers in your business, but that you've only ever seen 105 people using it at once. If the licence conditions state that you require a licence for each computer that the package is installed on, this means you need 200 licences. Such a policy is understandable, because although the user may not be physically "using" the software, there may well be one or more small components that are always running in the background so if all 200 machines are turned on, there are always 200 copies of these little widgets running concurrently. The solution? Well, there are several: (a) implement a mechanism that physically installs the software each time the user needs it, and de-installs it when they're done; (b) sweet-talk the vendor to see if they'll offer a concurrent licence; or (c) buy 200 copies, not 105.
Although the wording of the licence often ties your hands, concurrency-wise, it can also work in your favour so long as you can be bothered to read it. Ever read the End-User Licence Agreement for Microsoft Word, for example? (Correct reply: "Of course I have, as I'm legally bound by it and both my company and I can be prosecuted and fined for failure to comply"). Right up there near the top of the EULA of a copy of Word 2003 is the clause: " You may install an additional copy of the Software on a second, portable device for the exclusive use of the primary user of the first copy of the Software". Yes, really if you have a user with a desktop computer and a laptop, you only need one licence. Such clauses aren't as unusual as you'd think so it pays to read the licence, as there may be some financial saving in there for you.
Concurrent licensing can save money, but don't just leap into it without considering the alternatives or the issues. Before you take the plunge, ask whether there are other ways to license the products you're concerned with. And read those licences you may well find something nice buried in there.