Yes, you're absolutely right about the https issue - it's because
isacommons.org is hosted by GitHub, and they have a well known issue with using custom domains and https with their hosting. The Chrome warning (if you expand the 'Advanced' bit) says the https certificate belongs to GitHub, but the domain is
isacommons.org, hence the warning.
I'll make sure any references to
isacommons.org at the moment reference the http only link, and will find out if GitHub are addressing the https issue.