This is isakmpd, a BSD-licensed ISAKMP/Oakley (a.k.a. IKE)
implementation.  It's written by Niklas Hallqvist and Niels Provos,
funded by Ericsson Radio Systems AB.  Currently it is work in
progress, although it can be used for real setups.  There are
releases, but this distribution is not a release and is not named with
ordinary version numbers.  When you got the source, hopefully the
archive was named with a date which reflects when it was created.
These archives are also known as snapshots and will be created at
irregular intervals and put up on ftp.gsnig.net and ftp.appli.se in
/pub/isakmpd.  From Nov 14, 1998 isakmpd is also available in the
OpenBSD main source tree under src/sbin/isakmpd, though slightly
modified because I don't want to carry support files for other OSes in
that distribution.  Look at http://www.openbsd.org/ for details on how
to get OpenBSD source.