Osmo exports tasks to ics files using VTODO in BEGIN and END fields for tasks. This causes the import to many calendar applications to fail (Owncloud, Google Calendar) silently (events are imported, but not displayed).
Replacing all occurences of VTODO with VEVENT in the ics file befoire importing it to a calendar solves the issue.
Osmo should use VEVENT consistently in ics exports. VTODO may only be used for events that don't have valid BEGIN and END times.
Thanks for reporting. Fixed in SVN.