Under Fair Use guidelines people have the legal right to use copyrighted material if it meets certain guidelines.
If your use of copyrighted material falls under this then you do not need permission to use something from the copyright holder.
These conditions are:
the purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes;
the nature of the copyrighted work;
the amount and substantiality of the portion used in relation to the copyrighted work as a whole; and
the effect of the use upon the potential market for or value of the copyrighted work.
In some situations Fair Use might even include Parody or Satire.
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