@Garagecoder, PhotoComiX : To be honest, I'm not sure that coding a specific GUI for G'MIC is really a good idea. For instance, when using the GIMP plug-in, I'm often using also some of the GIMP native functionalities to achieve some of the effects I want to render. I believe that if someone starts a G'MIC-based GUI, he will one day have a need for interactive painting tools or something equivalent, and will end up in coding a brand new painting software :p
To me, it seems more reasonable to try integrating G'MIC into an existing painting software. It has been done not too bad for GIMP, and personally the next target I'd love to see would be Krita (
http://krita.org/).
It becomes a serious competitor to GIMP, already manage 16bits/channel images, and is coded in C++, so it would perfectly fits the requirements to host a G'MIC-based plug-in. Moreover, I already had some e-mails with the main coder of Krita, and he would be probably interested by some of the G'MIC functionalities.
The only thing I'm not really sure about, is if it has a nice plug-in API.
My dream would be to see someone porting the actual G'MIC for GIMP plug-in to Krita. This would be a new interesting interface for using G'MIC stuffs, with a nice painting environment, probably much better than any new GUI designed only for G'MIC, IMHO.
EDIT : They just have announced the creation of the Krita fundation. I'm really enthusiastic about the project, and subscribed to their Flattr channel, so I'm donating a little bit of money each month (not so much, as my current Flattr account for G'MIC has only few euros on it, but still, this is a symbolic donation :p ).