OpenBSD's native ntpd was written by Henning Brauer and Alexander Guy in 2004.
It has seen improvements from many others as well. Please see the commit logs
for an exhaustive list of contributors.
Portable OpenNTPD versions 3.9 and earlier were developed by Darren Tucker,
with contributions from Christian Weisgerber, Jason Mader and Anthony
O.Zabelin., and were based heavily on OpenSSH portable. It also has seen
improvements from many others. Refer to the commit logs for an exhaustive list.
This new portable version is based on the LibreSSL portable framework by
Brent Cook. It includes patches from FreeBSD, Debian and Gentoo OpenNTPD
packages, along with with compatibility code from the portable OpenSSH and
original portable OpenNTPD trees.