SEXTANTE

In case you're interested in running the last version of sextante in gvSIG build 1045 (1.1.2) you can use Mija's hack and check the log at ~/gvSIG/gvSIG.log in order to remove the conflicting libraries.
AFAICT it will be enough with the following:

cd '/Applications/gvSIG/sextante/gvSIG/gvSIG 1.1.2 build 1045.app/Contents/Resources/gvSIG/gvSIG 1.1.2 build 1045.app/Contents/Resources/Java/gvSIG/extensiones/com.iver.cit.gvsig/lib'

rm bsh-2.0b1.jar
rm jcommon-1.0.0.jar
rm jfreechart-1.0.1.jar
rm libDocEngines.jar
rm libMath.jar

DONE

You can keep you current version of sextante as well.

why should I?
For the first sextante comes with help in English.