There has been a lot of questions in regards to GMSC and the signing of Jar files so hopefully this article will clear up any questions.
GeoMedia Smart Client 2016 - The JAR files are signed with a time stamp and therefore will expire at the date defined by the time stamp on the jar file (currently with SP03 - Jan 18, 2028). Add-on jar files not delivered with the product will need to be check and if necessary signed again with a time stamp or a new certificate with a later expiry.
GeoMedia Smart Client 2015 - GeoMedia Smart Client 2015 SP03 has been released and all the jar files have be signed with a later time stamp. GeoMedia Smart Client 2015 pre SP3 will expire on December 22, 2016 so installation of SP03 is crucial and verification of add on's is also necessary. SP04 certificate will expire on December 30 2020.
GeoMedia Smart Client 2014 - The JAR files are signed with no time stamp so will the JARS will expire on the date specified by the certificate which is December 23rd 2016. GMSC 2014 is no longer supported so there are 2 options for re-certification
The organization whom requires GMSC 2014 signs the Jar files themselves.
When in question, verify the time stamp and certificate of the JAR file by using the keytool ( -printcert -jarfile signed.jar ) delivered with Java or the jarsigner (-verify -verbose -certs signed.jar).