The remains a nostalgic relic of a time when mobile users were desperate to break the walls of "walled garden" operating systems. While the "magic button" that turns Symbian into Java never perfectly existed due to architectural differences, the pursuit of these tools helped foster the mobile modding community we see today.
Search for embedded Java resources (many Symbian apps actually bundled a Java version for compatibility). Repackage those resources into a JAR container. Finding a Converter Today (Legacy Emulation)
These ran on the Java Virtual Machine. While they were more limited in hardware access, they were "write once, run anywhere," making them the most compatible mobile format in history.