The Netezza jdbc driver can be used on Mac. One way to test out to make sure that you are able to connect is to use the test functionality in the jdbc driver itself.
CLASSPATH=/path/to/driver # $CLASSPATH/nzjdbc3.jar should exist
java -jar $CLASSPATH/nzjdbc3.jar -t --host <host> -u <user> -db system
This will test out that the connection is working and there are no other environmental issues. At that point, check to make DBbeaver has found the jdbc jar file
Click "Add File" and then "Find Class"
Click on Add File and then Find class to make sure Netezza jdbc driver and class is found correctly.