This document describes several possibilities how to forward the URL for your OXID eShop into the source/ folder.
similar to https://mysqldumper.jira.com/wiki/spaces/OTC/pages/11665436/Installing+manually
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteCond %{HTTP_HOST} .* [NC]
RewriteCond %{REQUEST_URI} !source/
RewriteRule ^(.*)$ source/$1 [L]
</IfModule>
Additionally, you have to add a line to config.inc.php in source folder:
$_SERVER['SCRIPT_NAME'] = str_replace('/source', '', $_SERVER['SCRIPT_NAME']);