Agreed, this "modding etiquette" rules is something initially designed to give modders credit for their job, but it has developed in a way that it becomes a show stopper for further free & independent game developements. (yes, i know they will claim they stop nothing and that modders are still independent, but we all know what I mean)
If anyone makes a mod of a mod he is in his right to share his work (after mentioning due credit to the original modder) and the community has the right to download it at their own risk.
This issue of having to submit a permission request is sort of ... well.... let's keep it civilized!.
I sincerely think the GWX crew, despite deserving everybody's gratitude for what they have done for the game, should consider also how they handle this issue.