Reading the complaint, it's clear their focus is not on generic tracker source code but on copyrighted file metadata being preloaded into the tracker source code:
> The identified files and code are preconfigured to find and provide infringing copies of our Members’ film and tv content to Nyaa.si users in violation of copyright law.
> The identified files and code are preconfigured to find and provide infringing copies of our Members’ film and tv content to Nyaa.si users in violation of copyright law.