It's the work of Topher Grace of That '70s Show fame, apparently. The actor, and sometimes amateur editor, threw the video up on his Facebook fan page with this message.
I edited all the Seinfeld scenes from Curb season 7 into one episode. It’s more like a radio play, but if you sew together all the dialogue from audition scenes, read-throughs and rehearsals together… a 9 minute hint at what the plot of a reunion might have been.
It seems that Topher, much like all humans on earth with half decent taste in '90s sitcoms, is still thirsty for more of that iconic show about nothing. The footage and audio will be familiar to anyone who watched Season 7 of Larry David's HBO series Curb Your Enthusiasm (the sitcom methadone that has been keeping us sane since our Seinfeld fix has gone unanswered). That season featured a plot about David trying to put a Seinfeld reunion together, not because he really wanted to do it, but as a way to scam his way back into his ex-wife's life.
It's not Grace's first attempt at a little unauthorized editing. A few years back he reportedly edited all three of (trash) Star Wars prequels into one, 85-minute movie, although that cut has never been seen outside of Grace's own home.
The result of Grace's Seinfeld edits isn't perfect, but any Seinfeld is better than nothing. We'll go back to reading @Seinfeld2000's tweets, and waiting for another season of Curb now.