A prompt: the application X11 couldn't be opened. Can anyone help how to fix this? Thanks!

Try that?

In El Capitan, I kept getting the X11 error no matter what I did.

I finally got TA working. Here's how I did it:
- Launch the game while holding the alt/option key (this should bring up a wineskin window)
- Click "Set Screen Options"
- In the "Other Options" section (lower right), there's an option: "Use Mac Driver instead of X11". Make sure it's selected.
- Click done
- Quit the wineskin window.
- Launch the game normally.

Hope this is helpful.

Use the portingkit to update any game its easy and simple:
https://youtu.be/ZXz8J74Cyvc

Thanks mate, I tried your suggestion but still not working..

You guys should check out this thread on TAUniverse: http://www.tauniverse.com/forum/showthread.php?t=44866
It even allows Mac users to play online.