Rather than using concrete, our walkways are also pervious.  First, we reused pieces of old sidewalk that were broken to put in our new sewer line (top left), then for the remaining walkways we purchased a slate which came from eastern Washington.  Of course, these aren't as pervious as the Ecostone driveway, but they're much smaller areas, and we left pretty sizable cracks in between the piece which ultimately will be filled with tough groundcovers, likes mosses and thyme.

By reusing concrete, we not only saved money, but we kept it out of the landfill.