In order to run the Mod Uploader under Linux, you need
 * Linux 64-bit with glibc >= 2.14
 * QT >= 5.1.1 installed

Also, make sure the Steam client is running.
Run the Mod Uploader by executing "moduploader".
(for example, open a terminal in this folder 
 and type "./moduploader", followed by the return key)