We have now updated the dhclient and dhcpd man pages (section 8)
to mention the two DDNS ports.  We shall keep this ticket alive in
order to track adding an option to enable or disable DDNS during
run time.

The changes to the docs will be released in the next release of
the code - barring any problems this will be 4.3.3 and 4.1-ESV-R12.

thank you for your report,
shawn