More specifically, I think the part that seems copied is at 2:13 of the original[2], as it leads into a solo-ish bit which in the AI version sounds similar still, but goes on to do its own thing:
The only things they have in common are vibes (in the contemporary sense, not vibraphones). Two dudes singing about sex in falsetto at 120bpm over prototypical R&B/funk elements isn't special. If that's the bar for copyright infringement then 99% of the popular music canon is illegally-derivative. Marvin Gaye was a singular talent but that doesn't mean that his heirs should be able to collect money every time somebody plays an electric piano bassline and sings about making whoopie in alto II.
1) They had a musician come in and deconstruct the songs, and she showed that many of Blurred Lines elements copied the “rhythm” and “feel” of the sheet music, not the master recording.
2) Robin Thicke said in an interview he told Pharrell they should make something with the groove of Got To Give It Up.
As a non-musical person in a jury, those points are convincing enough that there was intent to copy the song even if the final song is clearly different. Though, it should never have been down to a jury and judge to decide.
Even more hilarious, a couple of years ago the Gayes tried to sue Pharrell because of an interview where he mentioned again Got To Give It Up was inspiration for Blurred Lines. Luckily that failed, but they definitely have it in for Pharrell it seems.
The closest thing I've seen is virtual drummers in Logic X which will follow along with the structure of your song and generate a percussive accompaniment. It's no substitute for a real drummer but it's serviceable.
One of the most fun things about jamming with other musicians is that things change with the ebb and flow of the band's energy. i always miss it when I'm just fooling around at home with a looper.
i could see something like this baked into an editing tool that allowers video editors to specify a tone or style of music in plain language to serve as background music.
No real clue how someone would use them for a more serious endeavor, only thing I could imagine would be to quickly iterate/prototype with song structures on a fixed seed to generate ideas for a real composition. Consider the case of an indie game developer or film maker getting some placeholder music to test the experience during early throwaway iterations.
i kept plucking away at it until i got it to a point where it could generate sheet music and guitar tabs in the style of various artists.
would be fun to revisit that project with fresh eyes.