If we define proprietary software as what it is not, it refers simply to software programs that do not fit the definitions of free software made by Free Software Foundation (FSF). FSF defines the term free software as: a software must allow anyone to use, reproduce, distribute freely the original work along with any modified derivative works, regardless whether a fee is charged, and the source code of the program must be provided as only with open source code can the users modify the program. In contrast, proprietary software covers software programs that do not open the source code and shareware programs that allow distribution but do not provide source code for download. It also covers “shared source” software programs that give users read-only access to the source code under specific conditions but do not allow users to perform modifications or further distribution. The term proprietary means “privately owned and controlled.” On the other hand, authors of free software program still possess copyrights. It is just that they adopt licensing terms with unspecified licensee that exercise a relaxed control over the way the software program can be used. If the term “proprietary” is used in a free software license, it simply means what does not fall within the category of free software.