Autodesk introduced 1 serial number for multiple copies a few years ago even as stand alone.
I doubt you can know if its legal other than getting a number and asking Autodesk they are very aggressive about pirate copies.
There was snoop software out there by Autodesk but it seems to have disappeared, ran across networks, so for my ex workplace with like 600 pc's could find all Autodesk product. Wanted to do it but could not find to confirm users and versions all legit software.
Is it a security thing for your code there is various ways of checking other than pkser.