Well known examples of proprietary software include Microsoft Windows, RealPlayer, iTunes, Adobe Photoshop, Mac OS X, WinZip and some versions of Unix.
Some free software packages are also simultaneously available under proprietary terms. Examples include MySQL, Sendmail and ssh. The original copyright holders for a work of free software, even copyleft free software, can use dual-licensing to allow themselves or others to redistribute proprietary versions. Non-copyleft free software (i.e. software distributed under a permissive free software licence or released to the public domain) allows anyone to make proprietary redistributions.
Some proprietary software comes with source code or provides offers to the source code. Users are free to use and even study and modify the software in these cases, but are restricted by either licences or non-disclosure agreements from redistributing modifications or sharing the software. Examples include Pine, the Microsoft Shared source licence program, and certain proprietary implementations of ssh.
Shareware, like freeware, is proprietary software available at zero price, but differs in that it is free only for a trial period, after which some restriction is imposed or it is completely disabled. Proprietary software which is no longer marketed by its owner and is used without permission by users is called abandonware and may include source code. Some abandonware has its source code placed in the public domain either by its author or copyright holder and is therefore free software, not proprietary software.
For certain proprietary software where the user can access source code, such as online applications (such as Internet forum software) or Java applications (where the source can be obtained by decompiling), some developers will obfuscate the source code in order to make it difficult for users to obtain the original code.
Answered by
Alok Gupta
at
4:21 PM on December 15, 2008
