The "client only" is kind of a misnomer. It means that two Service Broker services that exchange services must route the message through at least a higher edition version. An Express Edition cannot exchange messages with another Express Edition unless a Standard (or higher) edition server routes the messages between them.
While this is educational, is also completely irrelevant for you since Query Notifications (the feature behind the SqlCaheDependency modus operandi), never has to send a message remotely to another SQL Server instance. Is all local, so the 'client-only' restriction never applies. To be 100% accurate I should add that the way SqlCacheDependency uses Query Notifications never requires remote messaging, but this is splitting hairs.
I recommend you read the article linked, your post shows quite a few misunderstanding on how this technology works.