I heard someone say; "I used to work with you for free. Now I'm gonna do it pro bono" And I thought he just repeated himself. But I want clarity. So what does pro bono actually mean?
My understanding is that "for free" is simply "for free", but pro bono publico refers to a subset of free work aimed at certain recipients, specifically those unable to pay, or charitable, civic etc. organizations on behalf of such people, or (to a lesser extent) a worthy organization of limited means for free or reduced rates. So working for Bill Gates for free would not be pro bono work, since he has no problem with means.
"Pro bono publico" == For the good of the public.
It's normal usage is in the context of legal services provided for free, as in: