I have managed to build Xvnc on HPUX but only with some ugly hacking of
the X tree.  The X tree I used as the basis for the build is the XFree86 4.2.0
tree.  The XFree86 4.3.0 tree is unsuitable as it seems to have had some HPUX
stuff removed from it.  I built using the aCC C++ compiler.

Set the following environment variables:

  % CXX=/opt/aCC/bin/aCC
  % CFLAGS="+DAportable"
  % CXXFLAGS="+DAportable -AA +W749 +W740"
  % BOOTSTRAPCFLAGS=-Dhpux
  % export CXX CFLAGS CXXFLAGS BOOTSTRAPCFLAGS

Build the main part of the VNC distribution as normal:

  % ./configure
  % make

Unpack the X tree and apply the patches in xc.patch:

  % gunzip -c X420src-1.tgz | tar xf -
  % patch -Np0 <xc.patch

Then additionally apply the patches in hpux.patch:

  % patch -Np0 <hpux.patch

Finally try building the X tree:

  % cd xc
  % make World

If it all goes to plan you will be left with Xvnc in xc/programs/Xserver.  You
will probably have to modify the vncserver script to set up a sensible font
path, since many of the font directories on HPUX are different from the
defaults compiled into Xvnc.

If anyone can find a neater way of building a VNC-compatible X tree on HPUX
please let us know (see http://www.tightvnc.com for contact details).