Etienne,
This feature ( download Shibboleth2.zip configuration file ) is actually for 'Generate' scenario:
- You have one SP where you are going to configure and install Shibboleth SP to protect it's resource.
- If the above case is true.. only then you should use this feature.
- In order to 'get' the shibboleth2.zip file, you just need to provide the SP's hostname where you are planning to configure Shibboleth SP.
- So..you provided the hostname and use 'Generate' method and Gluu Server will 'generate' couple of configuration files ( with the help of your provided hostname + SAML cert if available ) which you will use inside of your Shibboleth SP server to quickly configure it with Gluu Server to make the SSO.
As you already have metadata from your SP and most probably you are using SimpleSAMLPhp to setup your SP... so it's not worthy for you to use these 'Shibboleth2.zip' files.