X11R6.8.1 can be found from the X.Org Foundation wiki at, and at mirrors of this server. Information about obtaining and installing binary distributions of this release can be found in the Installation Document. Information about obtaining the release in source form is given below.
The source for version 6.8.1 is split into seven tarballs:
X11R6.8.1-src1.tar.gz
X11R6.8.1-src2.tar.gz
X11R6.8.1-src3.tar.gz
X11R6.8.1-src4.tar.gz
X11R6.8.1-src5.tar.gz
X11R6.8.1-src6.tar.gz
X11R6.8.1-src7.tar.gz
The first three contain everything except the fonts and general X11 documentation. Those three are sufficient for building X11R6.8.1 if you already have a set of fonts. The fourth and fifth contain the fonts. The sixth contains the source for the general X11 documentation. The seventh contains the general X11 documentation in hardcopy format.
To format the X11R6.8.1 documentation use the latest version of our doctools package available from the Xorg CVS repository's "doctools" module.
The X source code for this and all releases/snapshots as well as development versions can also be accessed via the Freedesktop.org CVS repository. It's also possible to browse the freedesktop CVS repository. The CVS tag for this version is "XORG-6_8_1". The CVS tag for the stable branch for this release is "XORG-6_8-branch". To check out the latest development version, don't specify any tag.