GEM implementations are developed by J. Salvador Arias, you can mail me here: jsalarias at csnat.unt.edu.ar.
I will be happy to hear from you!, for any questions, suggestions, bug reports, your user experience or your code modifications. For bug reports, please specify how the bug is triggered, and if possible, send me a data set that produces the error.
Also, I will be happy if you send me or alert me of a pdf copy of your published results, your machine readable dataset, o any of program or source based on the method.