This is absolutely not true! The "source" is often minified JavaScript code, which is not the source code. In legal terms, it is a binary. It's a build artifact, the output of a program, not a human. Source code is the preferred form of modifying a program. The developers of a web application certainly don't use this form of their program when hacking on it. Giving someone a concatenated, minified version of a JavaScript web application is not giving them software freedom.

And even if the JavaScript files were not minified, they likely aren't available for user modification and redistribution because they are protected by copyright and a license that says "all rights reserved."