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What is a software license manger?

A software license manager is a software that helps you to protect your software from software piracy with so-called license keys or license files. A license manager is usually a software library which is linked to your software and which checks the validity of the license keys or license files. That is, when your software starts it calls the license manager, which in turns checks if the license (in the form of a key or file) the user has is valid. If the license is valid, your software runs normally. The license files can restrict the usage of your software in different ways:

These different licensing schemes are described in detail below.

Site licenses

A site license is the most permissive license type. With it your software runs on every computer at the site of your customer (with an unlimited number of instances). It is very easy to copy site licenses and use them at different locations, but the license file identifies the originating user.

Expiring licenses (time-limited licenses)

An expiring license (also called a time-limited license) limits the usage of your software up to a certain date. It is most useful if you sell your software in a recurring fashion (for example, if you charge for your software on a yearly basis) and want to make sure that your customers can use your software only for the paid time.

Fixed-node licenses

A fixed-node license restricts the usage of your software to a fixed computer. That is, with such a license key your software can only be used on the computer the license was issued for. This license type is quite restrictive for your users, but it is very simple and reliable way to protect your software from piracy.

Floating licenses

Floating licenses allow to use your software on an unlimited number of computers, but they limit the number of concurrent instances of your software. For example, if a customer purchases ten floating license, he can use only ten instances of your software at the same time. To use floating licenses your customer has to run a license server which manages the borrowing and returning of floating licenses. Floating licenses are a flexible licensing model, but the need for license servers make them much more error prone and complicated than the other licensing schemes. Therefore, floating licenses should be used with care and only in an enterprise context.

The different license types can usually be combined. For example, an expiring fixed-node license runs on a certain computer up to a predefined date.

Further reading

General things to consider in license management are described in "How to protect your software".

About Us

We are German software engineers obsessed with simple quality software. We developed the Zen License Manager (ZLM), a secure and easy-to-use license management solution.

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