What the heck is tightvnc 4.0? According to the TightVNC homepage and sourceforge page, latest stable is 1.2.9, and latest development is 1.3dev5.
It's an CVS ebuild, containing a beta version of vnc together with the CVS tightvnc patch for vnc-4.0. This version should be considered as obsolete as it's an ugly hack and it will be removed in the near future.