Latest version of Gemini Classic (1.6.2) released in 2016 supports the following versions of the OSX operating system: Mac OS X 10.7-10.9 and requires approximately 21 MB of free space on your hard drive.
As far as I know, the OSX 10.9 isn't supported anymore, meaning that it will receive updates on the installed Macs, but that's pretty much about it. I know for sure that 10.7 is completely discontinued.