tDOM depends on a full installation of Tcl. I recommend version 8.3.4 or later. It's safest to install from sources, which generally involves:
cd tcl8.3.4/unix ./configure make make install
cd tDOM-0.63/unix ./configure make make install
Sources specific to this article are in phaseit.net/examples/xslt.zip. Download them and unpack into a working directory. At this point you should be able to invoke
tclsh8.3 xslt.tcl example1.xml example1.xsl example.html
Notice that this creates example.html as an output.
Although binaries for Linux are available, in principle, most UNIX Tcl programmers have the habit of working from source. A consequence is that the source distributions, particularly for tDOM, generally are a bit better polished.
It's the opposite for Windows. tDOM works well under Windows, should you have a need for it there, and it's common to install a binary distribution on that operating system. See mini.net/tcl/tDOM for the latest information.