What characteristic would you say that people in the free energy community have in common?

To look at the part of the bigger picture (no one can really see the entire big picture ) and realize that the needs of the entire planet are dire and that something has to change if we are to take the next step in evolution.
Otherwise, this world will ultimately collapse and revert to some less modern level of civilization, or totally perish at our own hands due to carelessness.

Why do you think so few people either have heard about it ?

Numerous reasons: it's kept suppressed by those who's interests would be endangered by a proliferation of freely available energy. People could be "off the grid" and uncontrollable by the governments or the corporations who thrive on us "depending" on them (we truly do not have to depend on them).

Another factor is that people are not interested, for several reasons:
- many do not have time to engage in extra curricular activities because they are preoccupied with their own survival.
- others do not care because they have everything they need and do not wish things to change (change is hard to accept - always)
- third would like something to change but are unwilling to break their own small bubble and acknowledge there is world outside it, usually waiting for someone to do it first.
- fourth....

Why has "legitimate" science seemed to reject it?

The orthodox science has not rejected the concept. Many scientists are aware of these concepts but do not dare to peep about it because they would lose their grants and sources of funding, positions of statue, livelihood, reputation and prestige in the scientific community, etc.
Others are incapable to consider anything that they have not been taught or that's not in the orthodox literature right now and widely accepted. Their world is based on shallow theories that they regurgitate all the time because someone told them so and they blindly follow it.

How do you see the future, in the next ten years, for the free energy movement?

Nothing drastically will change in the next ten years. Our "Overlords" have a strong grip over this world and they will introduce change gradually and at their pace to allow them a transition from one economy to another, maintaining their control and power. History is the best indicator of how this was done (for example transition to Age of Pices, introduction of Jesus Christ and 12 disciples - basically Sun and the Zodiac, which was also present in previous cults of worship of the Moon, Sun, Saturn in prior Ages...).

If you observe what is going on today and has been for several decades (and will continue on in the future) is the introduction of the New Age movement which will pick up the pace and be the force of change between the Age of Pices and the upcoming Age of Aquarius.

How is important to the average person?

Not really or not at all. As I said above, most people live in their own bubbles, media induced filter inside their reality tunnels controlling what they perceive. Many believe what they read in the newspapers or hear on radio or tv and take it as a fact: "It must be true, the box told me..."
The Facts have been perverted so much by our Overlords that it is becoming quite difficult to discern what's true and what's not.

We will need a Renaissance of the mind for all of us first, a mental awakening and acceptance on many levels that there are other human beings living around us, that we are all equal and one and the same, and that we need to truly take care of each other. After that all the physical changes can happen in a blink of an eye, and I feel they will. But the doors need to open inside first for everything starts within and not without