Freeware is software that is available for use at no monetary cost. In other words, while freeware may be used without payment it is most often proprietary software, as usually modification, re-distribution or reverse-engineering without the author's permission is prohibited. Many types of software programs are offered as freeware, including games, utilities, and productivity applications. Freeware is usually distributed with a license that permits its redistribution to some extent, for example allowing users to give copies to friends. However, there may be restrictions, such as limitations on its commercial use. Some licenses permit the software to be freely copied but not sold. Another common provision is the prohibition of use by the military. Generally, freeware is a concise and limited version of a larger and paid software program. Two historic examples of freeware include Skype and Adobe Acrobat Reader.