About This File
From its thread on Lucasforums:
This utility will compare two GFF files and output the differences found between them.
There are two forms of syntax for this tool.
Syntax 1: no parameters (or launched directly via Windows Explorer)
This will call up a pair of Open File dialogs where you specify the two GFF files to compare. Then a Save As dialog will ask you where to save the output report.
Syntax 2: gffcompare.exe "file1" "file2"
This will compare file1 to file2 and send the output to STDOUT (which you can pipe or redirect).