Does this movie belong to Alien franchise?
The film started out as a prequel to the original Alien film.
Some recent history: there had been talks of a fifth Alien movie for years, with alternating contributions from James Cameron and Ridley Scott. In fact, Scott had committed to an Alien sequel or prequel about ten years ago, but aborted the project when the studio opted to make the AvP movies first, and Scott was no supporter of the Alien/Predator crossover franchise. After the disappointing box office from Aliens vs Predator: Requiem, the studio shelved the AvP franchise again to go back to the original plan.
The prequel film was supposed to cover the origins of the Weyland-Yutani Company. However, a full agreement could not be reached; Scott envisioned an explicitly R-rated movie, but since this would limit the target audience, the studio demanded a drastically reduced budget to which Scott wouldn't agree. So the Alien prequel film was abandonned in favour of an original project called Prometheus. Some ideas for the aborted Alien prequel would be used, and the story would contain elements reminiscent of the Alien backstory, but it would be a movie separate from the Alien Universe.
In an interview, however, Michael Fassbender confirmed that this is actually an Alien movie, taking place in the Alien universe.
http://moviesblog.mtv.com/2011/02/11...el-fassbender/. Ridley Scott was quick to retort, stating that "this is not an Alien prequel"; it does appear that Scott intends to make Prometheus completely different from the other Alien films. Exactly how is not yet clear, but it is likely that the story takes place within the same universe, but it is not directly connected to the events of the original.
There may of course be some misdirection on part of the film makers to help highten interest in the film.
According to Skymovies.com, there is a rumor that they are building a Space Jockey set, but no confirmation has been made yet. It has been confirmed that the Space Jockey will appear in this movie, and that the Alien will birth from the Space Jockey and will be different from the traditional Alien we've seen before. It will be a Alien and with Space Jockey DNA, just like how traditional Alien is an Alien with Human DNA and characteristics.