docbook2X uses a XSLT 1.0 processor to run its stylesheets. docbook2X comes with a wrapper script, db2x_xsltproc, that invokes the XSLT processor, but you can invoke the XSLT processor in any other way you wish.
The stylesheets are described in the man-pages stylesheets reference and the Texinfo stylesheets reference[1].
Pure-XSLT implementations of db2x_manxml and db2x_texixml also exist. They may be used as follows (assuming libxslt as the XSLT processor).
Example 1. Convert to man pages using pure-XSLT db2x_manxml
$xsltproc -o mydoc.mxml \docbook2X-path/xslt/man/docbook.xsl \ mydoc.xml$xsltproc \docbook2X-path/xslt/backend/db2x_manxml.xsl \ mydoc.mxml
Example 2. Convert to Texinfo using Pure-XSLT db2x_texixml
$xsltproc -o mydoc.txml \docbook2X-path/xslt/texi/docbook.xsl \ mydoc.xml$xsltproc \docbook2X-path/xslt/backend/db2x_texixml.xsl \ mydoc.txml
Here, xsltproc is used instead of db2x_xsltproc, since if you are in a situtation where you cannot use the Perl implementation of db2x_manxml, you probably cannot use db2x_xsltproc either.
If for portability reasons you prefer not to use the file-system
path to the docbook2X files, you can use the XML catalog provided
in xslt/catalog.xml and the global
URIs contained therein.
[1] The HTML versions of these documents
are not in the docbook2X distribution, because they are too large.
Your alternatives are: (i) use the HTML version on the docbook2X
Web site, (ii) use the Texinfo version that is distributed with
docbook2X, or (iii) generate the HTML yourself with the DocBook XSL
stylesheets. To do the last, simply type make html in the xslt/documentation/ directory.