Short answer...yes
Yes, you must install and enable OpenSocial
on the Domino server. For Notes, install the OpenSocial component,
which is installed by default if the user does not change the install options.
There are several reasons why this is
necessary.
In Notes gadgets that do not require
authentication can be rendered locally, but gadgets that require oAuth
(like IBM Connections) are rendered on the Domino server (or rather the
Shindig server running in Domino). In iNotes all gadgets are rendered
via Domino.
The main reason that Domino setup is
required is for security. An embedded experience runs active code,
JavaScript, etc, so it is very important that your administrator specifically
approve any embedded experiences gadget. This prevents potentially
malicious gadgets being rendered in your client. The approved gadgets
are pushed to the client via policy or selected from the MyWidgets catalog
by the end user.
Even if you're only using a URL Embedded
Experience, the same rules apply for the same security reasons.
To your last question, the code in Designer
that allows you to create an embedded experience is separate from the Domino
and Notes side code to render the embedded experience. And even if
it is all installed, to make it work you need to configure the correct
policies, MyWidgets catalog, etc. There is no error message, because
it is not an error condition. As far as the client is concerned,
it is not enabled for embedded experiences, and so it ignores the embedded
experiences MIME part.
I hope this helps.
Cheers,
Simon