In the real world, if I buy your branded building materials and, say, I build a house, you cannot by law restrict me from selling that house wherever I can - whether it is in a different state, or a different country altogether.
So why are building materials creators on the Internet allowed to restrict where on the Internet I use a finished product made of their building materials?
A lot of virtual world building material creators attempt to just do that, and the tighter their restrictions, the more their paranoia is evident. I will be the first to say that illegal copying/reselling of such materials is rampant on Second Life, and some other grids. Unless and until a permissions system is developed that can prevent such reselling, it will happen, and it doesn't matter how restrictive you make your license. All you can do is hope that others who see such theft will report it to you so you can file a DMCA takedown with the provider in question.
I, personally, don't happen to think that restrictive licensing will stop the illegal copy and reselling of such products. Where I have a problem is when I am using those materials in one world, and wish to sell the product in one or more other worlds.
As long as I am not attempting to sell your textures or sculpts as my own product, I don't agree that you have the right to tell me I can't sell a finished product containing your sculpts and textures on any grid I want. That's akin to building that house I talked about, in California, and you trying to tell me I can't sell that house in, say, Nevada. The finished product is mine, even if it contains elements you sold me. I should have the right to offer it for sale anywhere I like.
This doesn't mean I will ignore your attempts to restrict my use of said items. In most cases, I will be honest with you and say I am on Grids A, B, and C, and likely to transfer MY finished products between them. Quite frankly I'd like to see a court back you up if you tell me I can't do that, because you don't HAVE any rights over MY finished product.
Building component creators who use a healthy dose of common sense realize that a person's finished product is their own, and they have no rights to restrict the maker from selling that product wherever it might have a market.
There will always be those who try to say you can't make a product on Grid A containing their materials, and sell it on Grid B. This is a gross misappropriation of the nature of copyright and any court will tell them that. Rather, I'd like to see them study copyright - or better yet, get a copyright lawyer to help them understand that they really have no rightful control over a builder's finished product.