As of today Ground Zero Games is providing free PDF copies of their Full Thrust rules — the rulebook itself and both Fleet Books. While I own the three books mentioned in hardcopy, I will definitely download the PDF versions.
As to why the rules are now available for free — as are the other OOP rulesets by GZG — John of GZG mentions that the books are either out of print or getting there fast. I think the tacit acknowledgement is that the expected return from reprinting the books would be less than the cost of the reprint, hence this generous gift. Another factor in the decision might be the fact that GZG, as most miniatures outfits that produce rules and supporting miniatures, probably makes a lot more money selling the figures than the rules themselves (a business reality that GW was probably one of the first to recognize and use to great advantage), so giving away the rules once they are no longer profitable makes good business sense.
And as an aside, this is the 100th post on Tiny Tin Men. Congratulations to us :)