The Warranty of Noninfringement

Another important aspect of the MIT license is its disclaimer of the warranty of noninfringement . This concept is entirely missing from the BSD license. Here's how the MIT license says it (converted from uppercase letters ):

The software is provided "AS IS", without warranty of any kind, express or implied , including but not limited to the warranties of merchantability, fitness for a particular purpose and noninfringement. ( MIT license third paragraph.)

You can infringe someone's intellectual property by exercising any of the exclusive rights of the owner of that intellectual property ”copyright or patent ”without a license to do so. If you copy, modify, or distribute copyrighted software without a license, or if you make, use, sell or offer for sale, or import a patented invention without a license, you are an infringer .

Infringement can happen accidentally , but infringers can be penalized even if the infringement is not intentional. If software that you use infringes someone's intellectual property and you have no license to do so, a court may assess damages and order you to stop the infringement, no matter how costly or disruptive that may be to your business.

Infringement may not be the fault of the licensor who distributed the software to you. A patent owned by some third party of whom neither of you were aware may suddenly be asserted against all users of the software, including you and your distributor, and suddenly you can find yourself accused of patent infringement. As for copyrights, to your own and to your software distributor's surprise, some third party may assert that somewhere in the chain of title to the software someone made a mistake or committed a fraud, turning what everyone thought were legitimately licensed copies into infringing copies.

Warranting against infringement is an impossible burden to impose upon an open source licensor who is, after all, giving software away for free. No open source license provides a warranty of infringement. Neither, for that matter, do most proprietary software licensors, because the uncertainty and potential cost of infringement are far too expensive a risk to take. Even those few software companies that do provide a warranty of infringement typically limit their liability to the purchase price of the software; this is a trivial amount considering the potential costs of infringement.

Even for open source licenses that don't mention the warranty of noninfringement, the "AS IS" phrase should warn you that a meaningful warranty of noninfringement is simply not available. Where it is critical to your business that you avoid infringement risk, you must accept the burden to perform your own diligent analysis of the chain of title, or purchase your own insurance policy to protect you. It is foolish to look to typical software licenses ”and certainly to open source software licenses ”to eliminate your risk of copyright or patent infringement.