If you simply redirect the logo URL to your main site , it becomes difficult to navigate inside discourse for your users
You can use this plugin Branding - Custom brand header with logo, navigation and icons to add an header with your Affectiva logo (to your main site) and then remove (and the “home” icon appears and replace the missing logo) or choose another logo to your forum
See the header of this site in action for example https://forums.envato.com/