I'm building this test environment using jikes and optionally javac.
No ant.

The files are compiled in the source tree and the classes are
collected under the build directory.  Although I have a minimal
requirement as yet for any of the support facilities that are provided
by the ant construction of the build sources, any that are required,
like setting version information, are done manually in the files under
the build directory.

Checkout the FOP_0-20-0_Alt-Design tag from CVS, which now includes
xalan and xerces.

To build, set the environment variables FOPDEV and JAVA_HOME.
JAVA_HOME should be the directory under which the jre directory
resides.  I have been compiling with the IBM 1.3 jdk under linux.
FOPDEV is the path to the xml-fop directory under which src and build
reside.  Then source the following files, found in the xml-fop/bin
directory, in order

. bin/.path.functions
. bin/fopdevenv

These are designed as Bourne and up shell files.  Unix only, I'm
afraid.

The fopcomp script (found in the bin directory) is designed to execute
from anywhere in the source tree where .java files may be found.
Make sure fopcomp is accessible via your PATH.  Then, e.g.,

cd src/org/apache/fop/apps
fopcomp Fop.java

Because the properties classes, and many of the FO classes, are never
named in the source, files in these directories must be specifically
compiled.  The Dummy class in org/apache/fop/fo/properties and
org/apache/fop/fo/flow exists to facilitate this.  They may be
compiled directly, or invoked indirectly by compiling with fopcompall
instead of fopcomp.

Note that, for now, the files from the conf directory are also
installed in the build/classes conf directory.  This messiness
will be cleaned up when I get to the point of setting up an
ant build environment.

Running.

Firstly, fix build/classes/conf/userconfig.xml.  It has examples of
command-line override values specific to my environment.  Sorry
about that.

N.B. As at the time of integrating this experimental code into the
CVS tree, running may well throw an exception.  The code has not yet
been comprehensively tested.  If you do see an exception, please send
the fo file to me.

The code doesn't do much as yet, but to see what it does get up to, I
use the extensions I have made to the config functionality.
userconfig.xml is duly noted as the default user config file in
config.xml.  In userconfig.xml I put my input mode, input file name
and output file name.  Everything except fo->pdf has been stripped
away at this stage, but it still has to be specified.  See
build/conf/userconfig.xml for the way I have set up my simple test
run.  I have a pre-constructed .fo file.  Note that no output is
actually produced to a pdf file.

To run, once my CLASSPATH environment is set up, I

java org.apache.fop.apps.Fop

possibly adding a -d flag.