Nope,
public repos have license, often open source licenses that state that you can freely use the code, or change it , but only if the resulting product will also be opensource.
Other licenses such as the MIT license require that you name the original creator.
You don't need to accept that license to download and read the code.
A license allows new uses that copyright would otherwise block. Some kinds of AI training are fully local and don't make the AI into a derivative work, so they don't need any attribution and you don't need to accept the license to distribute.
But no license (that I'm aware of) says "You are allowed to read this source code, but you may not produce work as a result of learning from it"; for a start, that would clearly be impractical to enforce.
Other licenses such as the MIT license require that you name the original creator.