Proprietary software is computer software with restrictions on copying and modifying placed on it by the creator or distributor. These restrictions are enforced by either legal or technical means, and sometimes by both. The most common form of technical enforcement is by releasing only machine-readable programs to users and withholding the human-readable source code. Means of legal enforcement can involve software licensing, copyright protection, and patent protection.
Closed source is a term for software whose license does not meet the definition of open source software. Generally, it means only the binaries of a computer program are distributed and the license provides no access to the program's source code, rendering modifications to the software technically impossible for practical purposes. The source code of such programs is usually regarded as a trade secret of the company. Access to source code by third parties commonly requires the party to sign a non-disclosure agreement.
If the proprietor of a software package should cease to exist, or decide to cease or limit production or support for a proprietary software package, recipients and users of the package can be left at a disadvantage and have no recourse if problems are found with the software. Proprietors can fail to improve and support software because of business problems. Companies also end their support for a product for business and organizational planning purposes. The consequence is also tied to enticing more to upgrade and pay for newer versions.
The practice is legal in most countries unless restricted by copyright or license. Some proponents of free software consider the practice immoral, and it was the impetus for the creation of "copyleft" licenses.