Does anyone know if it is possible to run python-gui apps, like wxPython, on a c9.io remote server? I have my home server set up with c9 via SSH, and no issues logging in and running apps in the terminal on the VM. However, when I try to run GUI apps, I get the following error message. 
Unable to access the X Display, is $DISPLAY set properly?
After searching and searching, I can't seem to find a guide or anything in the docs that detail how to set $DISPLAY in the script. X display is installed and active on my server, but I don't know how to configure the c9 script to access it properly. Any assistance would be appreciated!
I don't know if Cloud9 supports it but normally to run a remote GUI application you would have ssh forward the X11 communication over the ssh connection via a tunnel.  So basically the application is running on the remote system and it is communicating with a local X11 server which provides you with the display and handling of the mouse and keyboard.  
If you run ssh with the -X parameter then it will attempt to set up the X11 tunnel and set $DISPLAY in the remote shell so any GUI applications you run there will know how to connect to the X11 tunnel.  Bw aware however that this is something that can be turned off on the remote end, so ultimately it is up to Cloud9 whether they will allow you to do this.
Running Python GUI apps on C9.io