U.S. copyright law protects the source code of computer programs as literary works, and may also protect screen displays as visual arts works or audiovisual work. Terms such as “freeware” and “shareware” describe software distribution methods. Copyright law protects all software, unless the creator explicitly releases the work to the public domain, regardless of that software’s distribution method or cost to the user.
Public Domain Software
If a software creator expressly releases software to the public domain, that software is not protected by copyright law. The software documentation would explicitly state that copyright protection has been disclaimed by its creator. Public domain software, including “open-source” software, can be freely copied, shared, modified and used with no restrictions. Programmers who release software to the public domain usually provide little to no support for users who may encounter problems with the software.
Freeware is software distributed at no cost to the user. Copyright owners have the exclusive right to distribute copies of their work. However, copyright law does not require that copies be sold for a price. Thus, copyright law protects freeware, and its use is governed by a license. Typical freeware licenses dictate that users may not modify the software or sell copies to others.
Copyright law also protects shareware. Shareware provides users the opportunity to try software for free before deciding whether to buy it. Shareware may be a more limited version of the program available for sale, and is also restricted by license. Typically, the license restricts shareware users from modifying, copying or distributing the shareware in any way. Continuing to use shareware after the designated trial period is an infringement of the copyright in that shareware and may constitute piracy.
Crippleware combines elements of freeware and shareware. Crippleware is a type of proprietary commercial software and is protected by copyright law. The software's owner provides a limited version of the commercial software for users at minimal cost, but some functions of the software are disabled. The user has the option to pay the owner to obtain a code that unlocks the disabled functions, providing the user with a full version of the software.
People buy proprietary software either as physical media to install or as an Internet download. Copyright law and patent law protect proprietary software, and its use is governed by strict licenses. Proprietary software licenses typically forbid the user from copying, modifying, distributing, sharing or selling the software. These licenses also restrict use of the software, and may restrict the number of machines on which the user may install the software.