Before choosing a window manager or desktop environment it is important to be aware of the license under which it is distributed. Commercial licenses cover products that you have to pay for, so that is first factor to consider. Fortunately most of the window managers and desktop environments listed on this site are freely available. However being freely available is not the same as being Open Source - the source code may not be available at all, or there may be severe restrictions placed on what you can do with the source code.

If you wish to read more about these issues, a good place to start is the Open Source Initiative (OSI) site. This organisation has approved a number of licenses as being in keeping with their definition of "Open Source". Although you should always check the terms of any license carefully, you should pay particular attention to the terms and conditions of any non-OSI approved license to make sure it is compatible with your intended use of the program and/or its source code.

Here are the licenses used by the main window managers and desktop environments featured on this site. Firstly, those that are OSI approved:

And secondly, those that are not OSI approved:

Activity Rating

Another important consideration when evaluating window managers and desktop environments can be the current state of development the project is in, ranging from one that is stable and no longer being developed, to one that is undergoing rapid development with frequent new releases. To try to capture some of this information, each featured window manager and desktop environment has been given a current activity rating, based mainly on the frequency of recent releases, as described below.

Rating Explanation
High An active project, where an updated version has been released within the last 6 months or so, with fairly frequent releases before that.
Medium The most recent release was between approximately 6 and 18 months go, so either the project isn't being developed anymore, or as is quite often the case, just undergoing a protracted release cycle.
Low The project appears to be static, with no release for over 18 months. This could be due to a lack of interest, or it could just be that the goals of the project were reached and it is considered finished.