Clothing Creator A purchases these materials to use in their creations on SL. Later on, they establish a presence on Inworldz. Now, the TOS does not prohibit cross-grid migration, but CC A asks out of common courtesy if she can use these materials on Inworldz. Materials creator says sure, just stick to the original TOS.
CC A goes about happily creating things, including items she offers for free, with permissions set to copy only (meaning there is no possible way that the material creator's items could be had for free). Material creator decides to create a presence in Inworldz, and finds out about the free items, and throws a hissy fit.
"You're violating my TOS!!!!"
Um, no. CC A did not violate your TOS - the TOS she bought the materials under is the same TOS you have in force today. It still does not restrict cross-grid migration, plus you gave CC A logged permission to use these items in their Inworldz creations.
You don't have a case and if you keep bugging Content Creator A, you could be held for harassment.
If you want further restrictions on how your items are used, then write a new TOS, and apply it to all purchases from that point, forward. You are not entitled to just "say" something is different.