When user has java installed on RHEL from RPM, the alternatives system determines which java is used by default. In the normal case, user doesn't have JAVA_HOME environment variable set, still java works fine. But trying to use jsvc in such environment results in:
Yes, even help is not shown when JAVA_HOME variable is missing. To maintain smooth user experience, it is in my opinion necessary to make jsvc detect Java location when java is installed from RPM and JAVA_HOME is unset (be it sun, IBM or openjdk). As a minimum jsvc should be able to show the help message even if java is undetectable so that user can see the option -java-home which is an alternative to setting JAVA_HOME.
The fix might be as easy as patching jsvc to try /usr/lib/jvm/java or /etc/alternatives/java_sdk in case JAVA_HOME and -java-home are missing.
To be clear this issue affects equally our RHEL zip and rpm distributions. Marking as minor because workaround is easy.