Right, you had a question. If the teacher's use of the DVD qualifies under the face-to-face exemption of the copyright law (below), then it is not an infringement and you can disregard the "warning." (There is an exception, described below.)
17 USC 110 Notwithstanding the provisions of section 106, the following are not infringements of copyright: (1) performance or display of a work by instructors or pupils in the course of face-to-face teaching activities of a nonprofit educational institution, in a classroom or similar place devoted to instruction, unless, in the case of a motion picture or other audiovisual work, the performance, or the display of individual images, is given by means of a copy that was not lawfully made under this title, and that the person responsible for the performance knew or had reason to believe was not lawfully made;What if "no classroom use" is a condition of a license? There is an exception. Many companies have attempted to circumvent the copyright laws (some successfully) by forcing the consumer to license the work, rather than purchase it. However, in order to create a binding license -- one that permits a company to step in and stop so-called unauthorized uses -- the company needs to prove that the end user entered into an agreement. As we've mentioned before, the most effective end-user licenses (EULAs) require some type of actual agreement -- typically a click-to-accept checkbox or button. These mechanisms for "agreeing" come in many shades -- and courts have even enforced shrink wrap agreements in which tearing open the shrink wrap signifies that the end user agrees with the license. Check your method of ordering to determine if you agreed to any licenses and check the packaging for signs of a license agreement. As a general rule, the easier it is to demonstrate that the other party agreed to the terms and conditions, the easier it will be to enforce the agreement. If the license is part of the packaging, it should be prominent and obvious that breaking the seal enters the end user into a license agreement. Our gut feeling is that the "warning," by itself, probably has little legal effect.