If those to whom it applies can call it aloud to each other, in public, then yes, I believe you can use "nigga" freely.
Nigga carries more of a "homeslice, brotha, fuck yo couch" kinda vibe.
Quote:
Is it okay to use the word nigga? There is a porno DVD that has "negro" as a part of the title. As far as I know nigga is a softer word than a negro.