That depends on which version of HTMLDOC you are using. If you
use the commercial version of HTMLDOC from this web site, then
yes, you have to pay to use HTMLDOC. We sell HTMLDOC Basic along
with optional software support depending upon your needs.
The open source version of HTMLDOC from htmldoc.org is
provided under the terms of the GNU General Public
License and may be used at no charge. That said, since you
aren't paying for the open source software you do not receive
any support or warranty of any kind.
All purchases of the commercial version of HTMLDOC fund the
continued development of the open source version of HTMLDOC.