Proprietary software is Software that has restrictions on using and copying it, usually enforced by a proprietary. The prevention of use, copying, or modification can be achieved by legal or technical means. Technical means include releasing machine-readable binaries only, and withholding the human-readable source code. Legal means can involve software license, Copyright and patent law.

The term is used by the Free Software Foundation to describe software that is not free software. Technically, the term means software that has an owner who exercises control over the software. Thus, it can be used for all software that is not in the public domain. However, the FSF uses the term to highlight that the owner is of prime importance, in contrast to free software , where the freedom of computer users is of prime importance.

The term non-free software is used interchangeably and about as often. Richard Stallman sometimes uses the term user subjugating software , while Eben Moglen sometimes talks of unfree software . The term non-free is generally used by Debian developers, but they too sometimes talk of proprietary software . Open Source Initiative prefers the term closed source software .

Well known examples of proprietary software include Microsoft Windows, RealPlayer, Winzip, and Adobe Photoshop.

Free software and proprietary software are both available under different pricing models. Sometimes they re expensive, sometimes they cost nothing (such as freeware, shareware, and abandonware). The difference between the two is about restrictions, not price.

Microsoft s shared source initiative is an example of proprietary software that some people mistakenly believe is not proprietary software. The terms under which Microsoft makes source code available under this iniative are restrictive.

Some implementations of the SSH protocol are proprietary, others are free software. MySQL is simultaneously available under proprietary terms and under free terms.

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