If they don't want the Winamp name and/or logo used in forks, they can just add a branding guideline that tells people to rename any forked product and to not distribute any graphical or audio elements associated with Winamp.
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If they don't want the Winamp name and/or logo used in forks, they can just add a branding guideline that tells people to rename any forked product and to not distribute any graphical or audio elements associated with Winamp.