Open source inherently means you can compile the code locally, for free. You can’t necessarily redistribute it, depending on the license, but I’m not aware of a “you can compile this source for testing and code changes only but if you use it as your actual copy you are infringing” license.
Most free software is also open source and vice versa, but not all, the difference usually lies in the licence, this stackexchange answer gets it pretty well
According to the Open Source Initiative (the folks who control whether things can be officially certified as "open source"), it basically is the same thing as Free Software. In fact, their definition was copied and pasted from the Debian Free Software guidelines.