Aiding an abetting requires participation in the crime or encouragement to commit the crime to some extent. Simply saying how a crime can be committed is not aiding and abetting.

It's very similar (and in some cases exactly the same) as being an accessory to a crime.

If the Brady Foundation says that people are 3D printing lower receivers using design files from a specific fosscad site to create ghost guns, then someone does that in California, the Brady Foundation isn't "aiding and abetting."

The accessory example of the above scenario would be directly telling someone exactly where and how to to get the specific parts and files they need and encouraging them to do so in a jurisdiction where it's illegal with the direct intent of having them commit a crime.

Since the files are legal many places, as are the materials, it's almost impossible to prove a specific intent to violate the law. It's similar with TPB. MEGA got taken down because they directly hosted the files and specifically encouraged people to illegally pirate software using the site. TPB has never done either.