If you download one of those legacy (unsigned) applications, the Gatekeeper security feature may pop-up a security dialog that warns users against downloading non-signed applications from the Internet. However, our legacy products created before Mountain Lion's Gatekeeper feature was available are not signed. Adobe has added the Gatekeeper signing requirements to our currently shipping applications. For example, Creative Suite 5 and 5.5 aren't signed by the new Developer ID authentication and require a Digital Signature verification method. However, reading down the compatibility list, I note potential caveats with security and plug-ins. An Adobe technical note says that there are no CS updates needed for the system upgrade. According to Adobe, the company worked closely together to test Creative Suite with Mountain Lion.
