I want to know the answer to the following question:
What can products not use if they want to avoid infringing on patent rights?
All the background I'm provided with is that "In September 1998, the Fraunhofer Institute sent a letter to several developers of MP3 software stating that a license was required to "distribute and/or sell decoders and/or encoders".". Is that enough to answer the question?
Answer: no