The application binaries require an installed Java runtime engine which can be obtained from http://java.com/en/download if you do not already have Java installed on your computer.
The GUI and console applications are 'runnable' JAR files so providing you have a standard Java installation double-clicking on the JAR file should start the application.
If that fails, run the applications from the command line or a batch file (or shell script):
| GUI: | java -jar gqlx-gui.jar |
| Console: | java -jar gqlx-console.jar |
Additional command line options are documented in the GQLx reference manual and allow you (among other things) to set a default Google user ID and password.
A preliminary language reference and usage guide is available here.
The SourceForge project page is here and the the source code can be downloaded from here.