Hello!
It sounds like you are running a plugin that helps with making sure your links are SSL/https.
This is great! Because https is really important! But! It means you should consider that hosting links on your site to insecure content is ‘against the rules’ of the plugin (and also will cause errors in your console, in all likelihood) and, in the end, result in the image links failing. However, this is not a GeoDirectory issue, this is about your strategy for SSL on your WP website.
Image uploads are a supported part of GeoDirectory. Use them, and you won’t have this problem, as you stated.
Some advice: If you want your site to stop rewriting your links to https, then turn off your SSL plugin or prohibit users from adding links to insecure (non-https) content.