Free software is a matter of freedom not of price. So says the Free Software Foundation (FSF). Open Source Software although mostly free is slightly different. The term “open source” software is used by some people to mean more or less the same category as free software. Open Source Licensing does have some sort of restrictions placed on them as well as not accepting all free software. However, the differences in extension of the category are small: nearly all free software is open source, and nearly all open source software is free.