ok I found the solution.
you have to execute buildprep.sh within src/share/native/build.
This will build the tomcat-native.tgz. You have to extract the fetched sources.
change directory to tomcat-native and execute buildworld.sh.
within native-builds/i386/lib I executed. tar -cf - * | (cd /data/jboss-web/bin/native/ | tar -xvpf -)
to copy them over.
jbossweb 1.0.1-current is running fine on FreeBSD 6.1 with diablo-jdk 1.5.0_7