Get License Key or similarly unique license value from module context

I working on Maker support in my EtherNet/IP module and am wrestling with the E/IP specification's requirement for serial numbers.

When I issue an E/IP license for standard Ignition, the license includes extra details to supply a suitable serial number. This isn't practical for Maker edition (nor Edge, if I ever get permission for that), so I've been playing with alternatives for automatic SN generation.

I considered using part of the system ID (hashed) as the basis for this, but that doesn't yield a stable value in a leased system. I'd prefer to hash the CD Key to supply the pseudo-random part of the serial number, but I don't see how to get that now-a-days.