I find this really odd. You can sell public domain code if you want. It's in the public domain, which means you can do anything you like with it, including selling it without credit to the author (though this would be really bad form) or payment.
The only reason some companies won't touch it (as apparently in Jake's case) is because they don't want to take the risk of anyone claiming ownership and having to get involved in legal battles; also, some business types consider public domain to be a legal impossibility, believing that you can't give up your automatic copyright. However, if you have a clear statement from the original author stating that their work is in the public domain, there really shouldn't be anything to worry about.
Obligatory disclaimer: I am not a lawyer! This is not official BRL advice!
The only reason some companies won't touch it (as apparently in Jake's case) is because they don't want to take the risk of anyone claiming ownership and having to get involved in legal battles; also, some business types consider public domain to be a legal impossibility, believing that you can't give up your automatic copyright. However, if you have a clear statement from the original author stating that their work is in the public domain, there really shouldn't be anything to worry about.
Obligatory disclaimer: I am not a lawyer! This is not official BRL advice!