During the install, there is an option to make Ubuntu use only free software. Is there a way to toggle this option now that it is installed? Thanks.
This is most probably what is being referred to (see bottom right):
After installation, here's how you can manually toggle repositories on or off to mimic the "use only free software" option in the boot menu of the Live CD (chosen via F6). This answer does not get into the semantics (meanings) of "free" :)
It sort of depends on your definition of "free" (free beer, free speech, or free bird), and there are sometimes disagreements on the definitions.
The main setting you have is in which repository you use, stay with main and universe and avoid restricted and multiverse.
For a more detailed description of repositories see
Or if you want libre, see Trisquel . Trisquel is based on Ubuntu but uses only kernel and applications the FSF considers Free as in Freedom.