I'm trying to build a very simple GUI application that either (i) runs on a local Ubuntu 14 server, or (ii) that runs locally but can read/write data from this server. Multiple people will be using this implementation to make modifications to a very simple array data file. The final solution can either be a script, dynamic webpage, or precompiled program.
Writing an HTML file that uses PHP to read/write form data: PHP is not enabled on this server. HTML5 FileSystem API doesn't seem to do what I need it to (i.e. it seems to only sandbox IO).
Python: Tkl/Tcl/wxWidgets are not available on this server, and most of the people who will be using this won't have it available locally either.
Your server should have X11 forwarding. Here is a page with an introduction:
http://math.msu.su/~vvb/2course/Borisenko/CppProjects/GWindow/xintro.html
I don't recommend coding an X11 application from scratch; this will take a very long time. Use an IDE like QT creator or XCode to speed up the process. If coded in C++, the X11 application should not have compatibility issues like you do with Python and PHP.