Unless there is something esoteric about my environment that I am not aware of, the version command looks broken on octo in Linux, I am using the RPM package octopuscli-7.4.1-1.x86_64 on CentOS 7:
$ octo version
.4.1
Looks like a bug to me, I was going to open an issue on https://github.com/OctopusDeploy, but got redirected here by advice in the template of the create issue screen.