There used to be seven free, and now there are eight. Here is a link to the new one, and to find the rest and download them for free on your kindle, search for "star wars sith tribe" in the kindle store, and all eight free volumes will come up.
Description for #8:
It’s the beginning of the end for this epic series in the thrilling final eBook installment, Star Wars: Lost Tribe of the Sith #8: Secrets. Two thousand years ago, Commander Yaru Korsin braved mutiny and desperation—and inspired his shipwrecked Sith tribe to rise up, seize, and dominate the planet Kesh. Now a shocking revelation about those legendary ancestors has thrown the Sith into turmoil, pitting one against the other in ever-growing clashes that could bring about their downfall. With his city descending into chaos around him, unassuming archivist Varner Hilts sets off for the forbidden temple, home to the wreckage of Korsin’s ship, Omen. Outnumbered by ruthless Sith warriors . .. . .(continued on amazon)