This meaning is the meaning most people assign to free. This isn't a good thing for Linux or other programs that are licensed this way. In the late 1990's, worldwide attention began to be focused on Linux and software that ran under it. As a result, a group of people in the Linux community came up with the term Open Source to describe Linux and software like it. But Open Source was a good marketing term, and it stuck, especially in the press.
Authors still own the copyrights to their programs.
These terms have to do with the license under which software can be copied and modified. You have to include source code, or allow some easy way to get it. You can modify the software, and you're allowed to distribute them on the same terms as the original license. No matter who you are, what you believe or what you do, the license applies to you. No one you give or sell the program to has to sign any additional license to have the same rights you do.