In September 1998 The Open Group changed the copyright of X11R6.4 from the non-free copyright used for the initial release of X11R6.4 back to the old free X Consortium style copyright. Given the fact that our main development focus is on XFree86-4.0 and that the 3.3.x releases are intended mostly to fix some bugs and get out new drivers to the public, we opted not to include X11R6.4 in XFree86-3.3.x.
XFree86-4.0 will be X11R6.4 based.