That does not -- and should not -- immediately follow. If you consider your look and feel software to be your exclusive value-add, you are not a candidate for FOSS and RMS is irrelevant. The traditional SOAS advantage is availability and data access; having your client code freely available does not reduce either advantage. Accessing is not (should not) be equivalent to access.

If I had the front-end javascript source code to gmail or salesforce or basecamp, that would neither give me access to other user's data, nor give me free access. Proof: I do have access to their complete front-end source code, just minified. Having it more readable would just be convenient.

Minification / Obfuscation != Security. Don't put anything in your front end code that you would not want an adversary to read (true of the backend too, if perhaps less urgently).