There is a big difference between free software and open-source software. The biggest difference between them is freedom. Here is a quote by Richard Stallman, an American software freedom activist and computer programmer.
“Open source is a development methodology; free software is a social movement.”
Nowhere does it say you cannot make money, open-source software is software offered in source code, and it comes with certain freedoms.
The freedom to run the program, for any purpose
The freedoms to study how the program works and change it so it does your computing as you wish
The freedom to redistribute copies
The freedom to distribute copies of your modified versions to others.
“ Thus, “free software” is a matter of liberty, not price. To understand the concept, you should think of “free” as in “free speech,” not as in “free beer””
As long as it follows these freedoms are present, you could technically call it “free software”.
Free software saves consumers millions of dollars each year. Software developers publish their own software with open source licenses so that others may develop similar software, or understand its functions.
WordPress itself is one of the most commonly used blogging platforms used by over 202 million websites. One of the main reasons it is so widely used by bloggers is its support so many plug-ins because of its open-source license. Open-source licenses allow users to tailor the program to their specifics and to make the program environment work best for them.
Open-source software doesn’t quite offer the same level of polished functionality as commercial products but you are still really likely to find software out there that is perfect for your needs.