This is a tough question to answer in detail: I encourage you to browse yourself. (They are all on Github) but: The BF code base in itself isn't too bad. The AP one is very complicated, and difficult to navigate. The names and organization are confusing. Compiling is finicky and slow due to the tool system they use, and it requires Linux (Note: The compile target is embedded!). I PRed an update to the build instructions, but it was rejected.

For all of these code bases, there is minimal or no documention: Neither guides, nor code comments. The functions, structs, fields, etc have no descriptions of their purpose or use. The modules, where you would expect a description of their purpose and use, instead includes the same license text at the top.