> The law only cares if the tool was "primarily designed" or "marketed" or "has only limited non-infringing purpose."
The first two elements have a mens rea implication behind them: you have to demonstrate the intent of the developers. That RIAA's strongest evidence of intent is buried in a unit test, and this seeming intent flies against the evidence in the far more prominent README that is discussing its unsuitability for infringing content. Furthermore, they can also demonstrate from their own practice in history that they refuse pull requests and close issues were people are clearly trying to use it only for infringing use cases.
The first two elements have a mens rea implication behind them: you have to demonstrate the intent of the developers. That RIAA's strongest evidence of intent is buried in a unit test, and this seeming intent flies against the evidence in the far more prominent README that is discussing its unsuitability for infringing content. Furthermore, they can also demonstrate from their own practice in history that they refuse pull requests and close issues were people are clearly trying to use it only for infringing use cases.