nsd can't find libnsd.so (a new shared library in aolserver 4). You need to add /usr/local/aolserver/lib to your LD_LIBRARY_PATH.
root@dev:/usr/local/aolserver# export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/aolserver/lib
root@dev:/usr/local/aolserver# ./bin/nsd -t sample-config.tcl -u nobody -g -web