One reason I have been following this thread is I am interested to see what the final decision of slowpoke/ftb will be. It is a hard choice. On one hand you have the possibility of Greg throwing temper tantrums and negatively impacting modpack maintenance in the future. On the other hand there is a user base that is still interested in playing with GT. There is no real solution that doesn't negatively impact someone, so the "right" course of action is not obvious. I don't envy Slowpoke having to choose and take the heat for his choice.
As to the Greg vs. mDiyo debate, mDiyo is not blameless, he has been provoking Greg a bit. But Greg's actions have been much worse, mDiyo comes out far above Greg in this altercation.
There is also a thought that perhaps mDiyo's provoking was necessary. I think of a family gathering where there is the one uncle with very racist views. Is it best for everyone to be polite and do their best to steer the topic of discussion as far away from race as possible, or is it better to call the uncle out on his views and get the issue out in the open? I am not sure what the best answer is with respect to this GregTech issue. I would tend towards not confronting since it seems that most people agree Greg will not change his ways. On the other hand, there is the Tekkit example. Most users were likely completely unaware of the issues with mod author permissions until something like Sengir sabotaging bees in the pack brought it out into the open for the casual user. So this whole thing does bring some light on the difficulty in maintaining a modpack with GT, and to a lesser extent the mods mDiyo writes. Perhaps some users will take that into consideration when voicing their opinion on which mods the FTB crew should be putting their limited time in.
Multiple difficult ethical questions in this thread. That could be why it generates so much heat.
As for what I might do in Slowpoke's shoes:
1) Keep all the 1.4.7 packs with GT available, and maintained. At this point its unlikely that any new versions for 1.4.7 will come out, but if it does come to pass keep GT in and updated them as they would have been updated if this controversy never came up.
2) 1.5.2 wgt and ngt ... keep on with these as well, don't kick the wgt users to the curb overnight. Perhaps hold back a wgt update if needed to get a GT version that plays nice with the pack. And of course everyone is welcome to move to ngt if they wish to stop playing and supporting GT. Users can vote with their feet.
3) Future FTB pack. This is the tough one. 1.5.2 wgt might be the last official FTB pack. Would depend on what sort of demand for GT exists, and how much Slowpoke trusts Greg to behave in the future.
4) Future 3rd Party packs. The contents should be the responsibility of the third party maintainers. If they wish to put up with potential GregTech headaches, I don't think it is FTB's place to ban them.
I don't believe what mDiyo has done warrents the removal of his mods. Thus only GT is up for consideration on my chopping block