NDA

A non-disclosure agreement (NDA) is a legal contract that allows certain information to be read and used, but not disclosed to anyone else.

Developers are often asked to sign an NDA when working on proprietary software. NDAs represent the opposite software development model to Open Source and are politically opposite to Free Software.

NDAs play an interesting part in the history of GNU/Linux. Part of Stallman's frustration with proprietary software was the NDA, which he viewed as business taking away the intellectual wealth once shared freely amongst hackers. This eventually lead to the GNU project and the basic tools which, when combined with the Linux kernel, provide an alternative to proprietary software and NDAs.