I'm afraid this is definitely non-free. It forbids distribution of modified versions on several counts:
> The DNSsafe software cannot be used or distributed separately from the > BIND software. You only have the right to use it or distribute it as > a bundled, integrated product. > > The DNSsafe software can ONLY be used to provide authentication for > resource records in the Domain Name System, as specified in RFC 2065 > and successors. You cannot modify the BIND software to use the > DNSsafe software for other purposes, or to make its cryptographic > functions available to end-users for other uses. > > If you modify the DNSsafe software itself, you cannot modify its > documented API, [...] Richard Braakman
