You can show your personal DVD to as many people as you like, and the filmmakers encourage you to do so. However, in an institutional setting such as a high school or university, a different set of rules applies. Showing the film in these settings requires additional rights.
The Corporation is available for educational use. We have two DVD versions, one that comes with 5 short thematic modules teachers may find useful, as well as password access to a study guide. We recently created a second version, with the film shorter overall, and in three parts for better classroom usage. There is also a feature version of the shorter cut.
When an institution buys the educational version, that DVD comes with public performance rights, that is, the right for that copy to be shown to groups of students, over and over, till the messages of the film sink in and the world is saved.
Note: You or your school needs to purchase this version if you are planning to use it for classroom or other public performance uses. The home DVD is not licensed for these uses.