Installation download page http://getgreenshot.org/downloads/
I just went onto the main website (getgreenshot.com) and clicked the Download link.
It downloaded one file (Greenshot-INSTALLER-184.108.40.206-RELEASE) that Chrome immediately warned me could "harm my computer." It is not signed with the Greenshot cert.
I downloaded a second file by clicking the SAME Link, and it directed me to Greenshot-INSTALLER-220.127.116.11-RELEASE, which was signed and did not give a Chrome virus warning.
And here is the unsigned file location: