Consider adopting a personal policy of consuming only entertainment with a free (as in freedom) copyright license. Then, if you should become inspired to modify -- improve -- the entertainment you have consumed, producing a derivative work, you are free to do it right then, and not have to wait 95 years for copyright to expire (or not have to do expensive copyright licensing legal negotiations).
Don't put yourself in a position where you'll waste thought on something not will not be productive.
Inspired by the film Sita Sings the Blues, licensed Creative Commons later public domain.
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