When running Java applications on a *nix style of operating system that need to load native libraries, you will need to set the LD_LIBRARY_PATH environment variable (or something similar). That's not an issue on Linux.

macOS: I won't let you, it's for your own good

On macOS the System Integrity Protection (SIP) prevents these variables to be set in your shell (bash, zsh). It works inside Eclipse, when you define environment parameters, but not in any shell script. Unfortunately Maven's command line mvn is a shell script.

The Notes challenge

Since the Notes client is a cross-platform product, the library locations aren't where a macOS program would look for:

• The application directory. That's where the Java runtime is at home, not the notes executable
• In a library location, here looking for notes instead of libnotes.dylib
• /Users/[YOURNAME]/Library/Frameworks/notes.framework/
• /Library/Frameworks/notes.framework/
• /System/Library/Frameworks/notes.framework/

You could try to symlink the first library: ln -s /Applications/HCL\ Notes.app/Contents/MacOS/libnotes.dylib ~/Library/Frameworks/notes.framework/notes (after creating the rewuired directories) to run into the next challenge.

I wrote about more modern Java syntax and streams before.
There is more to it. Non Blocking I/O and Event Loops allow for
better performance. It's not a magic bullet, some readjustment is required

Adjusting methods, exceptions and return values

Initially it might look daunting, but the adjustments are not too big. Let's look at some examples. A classic Java method looks like this:

String someResult throws DidnWorkException {
    // Working code goes here
    if (someCondition) {
        throw new DidnWorkException();
    }
    return "It worked";
}

Its asynchronous counter-part looks like this:

Future<String> someResult() {
    return Future.future(promise -> {
        // Working code goes here
        if (someCondition) {
            promise.fail("It didn't work"); // Could use a Throwable too
        } else {
            promise.complete("It worked");
        }
    });
}