The download link points to Debian server, as the package on the original site actually is missing IPv6 support - while it claims to be version 2.4b2_to-ipv6, it's actually 2.4b2_to. Additionally, patches from Debian are applied to make IPv6 compile time flag, introduce source IP support, improve manpage and other things. To avoid conflicts with standard fping, this version is installed as fping6.