In general, a software license is thought of as “open source” if it allows people to use the source code and executable as described in this faq under “what is open source?”.

However, an organization called OSI has created a definition that tries to formally capture the principles behind “open source”. OSI maintains a list of licenses that it feels conform to this definition, and usually people think of these as being the archetypical open source licenses. So most often when people talk about an open source license, they are talking about one of the OSI approved licenses.

what is an open source license?