Opencast includes ORGANIZER only if there is a Presenter (DC Creator) in the metadata. So the lack of an ORGANIZER: field is not a problem to any existing CAs because Opencast allows scheduling events without a presenter name.
Second, Opencast's use of the ORGANIZER field in the ical feed is not standards-compliant. Specifically,
From a standards point of view, it makes no sense to identify the presenter as the ical ORGANIZER because the presenter is not sending a group scheduled event or publishing his/her busy time. If we think of the CA as the "user" it also doesn't make much sense because we're not using VFREEBUSY.
The fake ORGANIZER format used by Opencast can cause problems with parsing the feed for some CAs, especially when the presenter name includes quotes e.g.
This both has encoding issues (quotes within quotes) and also a non-compliant overlong line.
So simplest is just to drop ORGANIZER, as it's not meaningful or useful and can cause problems.
CAs that need the presenter info should get this from the attached episode.xml.
It turns out there is a side-effect from dropping this, which is that Galicaster no longer recognizes the event has having changed when its metadata changes (as it looks at SUMMARY and ORGANIZER in iCal fields).
Probably needs fixing on the GC side.
This change somehow got lost between 4.x and 5.x / 6.x / develop