Notable examples of proprietary software include Microsoft Windows, iTunes, Adobe Photoshop and Adobe Flash Player. Certain operating systems based on UNIX, which typically employ the open-source model, are also proprietary, including IBM’s AIX, Hewlett-Packard’s HP-UX and Sun Microsystems’ Solaris.
Proprietary software that includes free and non-free variants within its distribution is considered to be mixed-source. Most of the proprietary UNIX-based software normally includes open-source components, such as Sendmail, X Window System and DHCP, in addition to the closed and proprietary system utilities.
Companies don’t always charge for their proprietary software, although they lock access to the source code and impose restrictions on its use. Internet Explorer is an example of proprietary software that is available for free, while most other products offered by Microsoft, including its Windows family of operating systems and Microsoft Office, require a fee to procure a license. Oracle, Macromedia, Adobe and IBM are other companies besides Microsoft that almost exclusively produce proprietary software. The restrictions regarding the use of software are typically delineated in the end-user license agreement and the terms of service.
Industry analysts believe that the use of proprietary software is on the decline on account of the rising availability of open-source software that could potentially dominate the market revolving around operating systems and other applications in the future.