Apologies, I was not clear in that I do not plan to use the name, but you still provided the info I needed. Thank You.
I think, second guessing Bruce, that the rules themselves are public domain. I believe the expression of them in specific language may have been copyright registered back in 1966 and may have been renewed as then required by law. This needs to be clarified if you plan to replicate, say, the rules stuffed in the package.
Phillip is correct---while Twister may no longer be covered by patent protection, the rules are most likely covered by copyright.
Good point on the rules. You would need to determine if there was a patent and if that patent spelled out rules, as that might trump the copyright, if any one the rules. Regardless, there should be a way to rephrase them such as writing your own from scratch without reference to those from Hasbro/MB.
typo, "one" in line 3 of preceding comment should be "on".