Humans on NewEarth
How exactly did the humans get there? I cover it pretty extensively in the foreword of the first 3 books, but to sum it up a coorporation had been exposed for using unsafe environmental practices and having an environmental disaster on a planet they were harvesting resources from, so they set up an environmentally friendly project and recruited volunteers with the glowing promise of as much clean air and water as you can stand, all free for the taking. It was a publicity stunt that they made a tidy profit on, but claimed a loss of course.
Each couple was responsible for a minimum return of goods, harvested or produced to maintain contact with OldEarth, it was 50% of whatever they made. At the same time, they could claim as much of the resources as they wanted as long as they kept it environmentally responsible. Since the people they recruited were environmentalists, greenies, as they were called, they were pretty serious about that commitment.