Open Source Simply any Software whose source code is included in it or is available for free to anyone.WHAT OPEN SOURCE INITIATIVE Says:Open source doesnt just mean access to the source code. The distribution terms of opensource software must comply with the following criteria:1. Free Redistribution:The license shall not restrict any party from selling or giving away the software.2. Source Code:The program must include source code, and must allow distribution in source code as well as compiled form.
3.Derived Works:The license must allow modifications and derived works, and must allow them to be distributed under the same terms.5.No Discrimination Against Persons or Groups:The license must not discriminate against any person or group of persons.6.No Discrimination Against Fields of Endeavor:The license must not restrict anyone from making use of the program in a specific field of endeavor. 7.Distribution of License:The rights attached to the program must apply to all to whom the program is redistributed without the need for execution of an additional license.8.License Must Be TechnologyNeutral:No provision of the license may be predicated on any individual technology or style of interface.Open Source
Free SoftwareFree Software not equals = “Without Cost”An English dictionary lists almost twenty different meanings for "free". Only one of them is "at no cost". The rest refer to liberty and lack of constraint. When we speak of Free Software, we mean freedom, not price.A/C TO GNU Project:A program is free software if the programs users have the four essentialfreedoms:1.The freedom to run the program, for any purpose (freedom 0). 2.The freedom to study how the program works, and change it so it does your computing as you wish (freedom 1) i.e access to source code.3.The freedom to redistribute copies (freedom 2).4.The freedom to distribute copies of your modified versions(freedom 3).
Paid software refers to any Software or part of it which can be bought from the respective vendor of that software.Paid software is more familiar to general people but not due to the fact they have to buy it but due the reason they dont know about OSSstill they are using it.Now Paying for a software does not means it cannot be open source.Even paid softwares are open source.Paid Software