The jt-sde module requires the ESRI ArcSDE jars included with your software be installed in your local maven repository:

mvn install:install-file -Dfile=jsde91_sdk.jar \
   -DgroupId=com.esri -DartifactId=jsde_sdk \
   -Dversion=9.1 -Dpackaging=jar -DgeneratePom=true

mvn install:install-file -Dfile=jpe91_sdk.jar \
   -DgroupId=com.esri -DartifactId=jpe_sdk \
   -Dversion=9.1 -Dpackaging=jar -DgeneratePom=true

You can then build using the arcsde profile:

mvn -Parcsde

The default SDE version is 9.1. if you want to use newer ESRI ArcSDE Java API jars, provided that you installed them through mvn install:install-file in your local repo, run maven with:

mvn -Parcsde -Dsde.version=9.2