Hey Pyru, thanks for the lightning quick reply! Heres the output from the terminal.

YoungThugs-MacBook-Air:~ YoungThug$ java -jar /users/YoungThug/Downloads/RSCE_Launcher.jar

---------------------------------------
jagex.jag: 4445d7d9c1535a6f47a09ef33c02c15f
---------------------------------------
Landscape.rscd: 89b58a562a7274664f904728ed2c97c0
---------------------------------------
Sprites.rscd: 344072df0c561dfcafecf98b100be2e8
---------------------------------------
sounds.mem: 9c48528aa1856071bddd96f1ccf0280d
---------------------------------------
RuneScape.png: 95aa158aa270f2c321e43473d22e68ac
---------------------------------------
models.jag: 8ccaf87562b025d127ce55106b456a43
Exception in thread "AWT-EventQueue-0" java.lang.ClassFormatError: Incompatible magic value 1008813135 in class file sun/audio/AudioPlayer
    at java.base/java.lang.ClassLoader.defineClass1(Native Method)
    at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1007)
    at java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:174)
    at java.base/java.net.URLClassLoader.defineClass(URLClassLoader.java:545)
    at java.base/java.net.URLClassLoader.access$100(URLClassLoader.java:83)
    at java.base/java.net.URLClassLoader$1.run(URLClassLoader.java:453)
    at java.base/java.net.URLClassLoader$1.run(URLClassLoader.java:447)
    at java.base/java.security.AccessController.doPrivileged(Native Method)
    at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:446)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:563)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:496)
    at com.rsc.emulation.client.pc.b.<init>(Unknown Source)
    at com.rsc.emulation.client.pc.a.init(Unknown Source)
    at com.loader.rscemulation.util.a.u(Unknown Source)
    at com.loader.rscemulation.frame.a.a.actionPerformed(Unknown Source)
    at java.desktop/javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1967)
    at java.desktop/javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2308)
    at java.desktop/javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:405)
    at java.desktop/javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:262)
    at java.desktop/javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:269)
    at java.desktop/java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:297)
    at java.desktop/java.awt.Component.processMouseEvent(Component.java:6578)
    at java.desktop/javax.swing.JComponent.processMouseEvent(JComponent.java:3343)
    at java.desktop/java.awt.Component.processEvent(Component.java:6343)
    at java.desktop/java.awt.Container.processEvent(Container.java:2259)
    at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:4961)
    at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2317)
    at java.desktop/java.awt.Component.dispatchEvent(Component.java:4793)
    at java.desktop/java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4904)
    at java.desktop/java.awt.LightweightDispatcher.processMouseEvent(Container.java:4539)
    at java.desktop/java.awt.LightweightDispatcher.dispatchEvent(Container.java:4480)
    at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2303)
    at java.desktop/java.awt.Window.dispatchEventImpl(Window.java:2758)
    at java.desktop/java.awt.Component.dispatchEvent(Component.java:4793)
    at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:766)
    at java.desktop/java.awt.EventQueue.access$500(EventQueue.java:97)
    at java.desktop/java.awt.EventQueue$3.run(EventQueue.java:717)
    at java.desktop/java.awt.EventQueue$3.run(EventQueue.java:711)
    at java.base/java.security.AccessController.doPrivileged(Native Method)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:89)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:99)
    at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:739)
    at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:737)
    at java.base/java.security.AccessController.doPrivileged(Native Method)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:89)
    at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:736)
    at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:199)
    at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
    at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
    at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
    at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

Can you confirm which version of java you have installed, by typing "java -version" in your terminal, and then pasting the output here?

Thanks,
Pyru

YoungThugs-MacBook-Air:~ YoungThug$ java -version
java version "9.0.4"
Java(TM) SE Runtime Environment (build 9.0.4+11)
Java HotSpot(TM) 64-Bit Server VM (build 9.0.4+11, mixed mode)
YoungThug-MacBook-Air:~ YoungThug$

As I suspected.

You will need to uninstall the current version of java you have, then download and install JDK 1.8. Once you've done this, you *should* have no issues getting our game client to work.

Here is a link & instructions:

http://www.oracle.com/technetwork/java/ & 33151.html

Scroll down to " Java SE Development Kit 8u162", accept the license agreement, select MacOS and begin your download / installation.

Please post back here to confirm this resolved your issue.

Thanks,
Pyru

Hey Pyru, thanks so much!!

That solved the problem. Really appreciate your help and prompt answers.

Young Thug out!

I'm glad I could help you out and I hope to see you in-game.

Cheers,
Pyru