If you use Odoo.sh (Odoo’s PaaS), the Enterprise source code is automatically integrated into your builds. You don't need to manually download it; you simply manage your custom code in a separate repository that "links" to the Enterprise modules provided by the platform. Installation and Setup
Before attempting to download the code, it is vital to understand that Odoo Enterprise is not "open source" in the traditional sense; it is "shared source." Download Odoo Enterprise Source Code