Open Source vs Free Software

People use “open source” and “free software” as synonyms but are not. All Free Software is open source, but not all open-source software is free software.

Free software is free as in “free speech”, not as in “free beer”. That is the philosophy of Richard Stallman. I see it a bit differently.

To me, there is open source and closed source software:

• Open Source: I can read the source code. It’s available.
• Closed Source: I don’t have legal access to the source code.

Free Software is more than just Open Source

Interestingly, even if the source code is legally available for me to read, I might not be allowed to do anything with it. Essential rights I want to have are:

1. Copy: If I want, I can make a backup of the software for myself.
2. Modification: If something is broken or doesn’t behave as I want, I am allowed to change the behavior.
3. Derivative Distribution: I am allowed to distribute the software with my changes.
4. Choice of License: I am allowed to distribute the software with my changes and any license I want. That means if I want to sell it, I can.