I was right the first time, this three chapter manga is a prequel to the movie. Or, more like, a prequel, plus the first part of the film. The Plot from Wikipedia matches up with the first two chapters:
With their power dwindling due to the absence of their leader, the remnants of Frieza's army are led by an alien named Sorbet, who decides to revive their master. He then sets off to Earth with one other minion, Tagoma, where they convince Pilaf, Mai and Shu, who have collected the Dragon Balls to let them use them instead. As Shenron is unable to fully revive Frieza, he brings him back to life in pieces, and his minions put him together using their advanced technology. Once restored, Frieza kills Tagoma and learns that Son Goku got much stronger, to the point of defeating Majin Buu, and thus he decides he too needs to become more powerful. Frieza reveals that, since his power was inborn, he had never trained a day in his life, and so he trains himself for the first time before returning to earth with his army six months later. Jaco the Galactic Patrolman travels to earth to warn Bulma that Frieza is approaching, and she gathers the other warriors to fight him. With Goku and Vegeta training on Planet Beerus with Whis, unaware that Frieza has been revived, Gohan, Piccolo, Krillin, Master Roshi, Tenshinhan and Jaco fight off Frieza's soldiers.Anyway, with Chapter 3 we find out who was in the space ship from Chapter 2's cliff hanger. For more on Jaco, check out this post. It's pretty cool to see how he's fitting in to the DBZ universe.
Chapter 3 reads like the best of the DBZ anime. It's got me excited for the movie, which opened really well in Japan and has me hopeful to see the DBZ saga continue. These have been out for a while, but I couldn't find an English version anywhere, so I did the same thing here I did for Chapter 2.