Open source software is free.
Anyone can download an open source program. You can run it, copy it and pass it on to friends and colleagues. You can look at the code and see how the developers made the program. None of this means paying a license fee. It doesn’t break any laws. You have permission to do all these things.
Money, or cost, is not the most important point. Advocates think of word free as in ‘free speech’, not ‘no payment’.
Freedom means that users can change the programs to suit their own needs. That would be illegal with most other forms of software.
Open Source freedom means responsibility
There is one restriction: you must, in turn, pass the same set of freedoms on to everyone else. Altered open source programs must be made available to everyone.
This approach decentralises control. In turn, that means developers continually improve the software.
At the same time, having large numbers of people looking at and improving on programs means that bugs are quickly eliminated. That improves quality control.
A lot of important programs and applications are based on free software. It runs the internet and underpins some of the most popular operating systems.