I will never understand why 3rd party people (players/mod builders and so on) spend hours and hours working on games and upload it to the internet and say you can only use my work for this and that is it.
Anyone is welcome to do anything they want with anything I do. I just hope they can use or make it better. Now if they are making money off of it then that would be different.
Most folks, will give you permission IF you ask them directly and promise to credit them in an included .txt file or something, but don't just assume that they are free. Sometimes though, they may have spent enough of their own energy creating something that they want more than that OR have the vastly mistaken idea that the images, textures, etc are worth some sort of cash when in reality, few people would ever pay for something like that.. This particular subject has been beat to death multiple times here AND on the Skyrim site as well though.
In regards to your question about updating the files you placed on the vault, my personal opinion would be to actually update the versions that are already up there to keep them easier to manage. Now-a-days, folks generally are not using dial-up for internet, so file size is seldom an issue any more, where managing hundreds of possibly duplicated files would be a major pain in the arse.
