You need to obtain a key from Zero G Software in order to fully license your copy of InstallAnywhere Now!. The key file for IA Now! is free; simply go to http://www.ZeroG.com/ianow to obtain it.
See the section in the manual on redirecting your application's output.
See the section in the manual on Mac OS installers.
Since the "Other Platforms" installer is entirely coded in Java and does not have the benefit of a LaunchAnywhere executable to run it, it must be invoked like any traditional Java application. Java applications are invoked differently from operating system to operating system; see the instructions that come with your Java virtual machine for more details. On most systems, you can invoke the "Other Platforms" installer by first installing a Java 1.1-compatible virtual machine, then typing java -classpath install.zip install at a command-line prompt.
It's possible that you are loading class files dynamically, which InstallAnywhere's auto classpath detection is unable to detect. In order to make sure that the class files that are being loaded dynamically are found, make sure to put their containing folder on the classpath manually by selecting that folder, then clicking the "In Classpath" checkbox.