Both Header and Footer show this code only if you view source.
1 - Should this really be public information?
2 - Why is it in the header and footer?
1 - Yes: this is only informational log, most common on many others plugins.
2 - Most themes dont'have both or correct meta wp_header and wp_footer
This mechanism was created to more accurate assistance and to minimize unautorized and malicious versions of my plugins expecially from india ... the security key, based on MD5 Checksum, is, for now, only on a introducing phase, is not a sensible data and is related only to this plugin pakage and not to your WordPress installation or configuration ... if you are expert look at the contents of the entire package and you'll see more!
If you have others question sLa is very happy to assist you, but next time, before you post, please read the guidelines, otherwise your message will be dropped ;)
P.S. Nobody forces me to give assistance, and no one is forced to use my plugins :)