I’ve added a new widget setting to customize that url in this commit:
https://github.com/discourse/discourse/commit/02f771e66ead3fb6e861bfa1fd41d8c65d10ab1d
Here’s an example of how to use it via a customization:
<script type="text/discourse-plugin" version="0.4">
api.changeWidgetSetting('home-logo', 'href', '/new-url')
</script>
Just replace /new-url
whatever you want the path to be and you should be good to go.