Activity app: integrating RSS "sub feed"

I want to integrate an activity stream from the /owncloud/index.php/apps/activity/rss.php into Dokuwiki. The standard feed contains all activities of a particular user and is authenticated through the token. I want to have the RSS feed of a particular folder (and below), this folder is shared through group permissions/user permissions.

1. what is the best way to only get the activities of a particular subfolder?
2. How should this be authenticated when requested from another application outside OC? (but on the same server)
3. Is there any documentation aside from reading the code?

Thx, Thommie