I love "Song of the South" and have a copy I picked up in the UK (I can play it on a multiband VHS).
Although the time setting is somewhat ambiguous, it is not Antebellum. The word "slave" is never used; neither is the "N" word. Uncle Remus in fact prepares to leave the Aunt Sally's on his own - something he could not have doe as a slave.
It's a delightful movie with great songs, characters and pioneering live action/animation. In fact, Uncle Remus is the hero, with more sense than any of the white characters. Too bad Disney is so PC they would rather lose money by not selling the movie.
I agree, it is a good movie. But Disney would prefer that it didn't exist. I haven't seen the movie since I was a child, so I assume you are correct about it's ambiguity. Nevertheless, the stereotypes (real or imagined) terrify Hollywierd.