According to the Horde wiki link, it looks like the later versions of Kronolith (2.2) support application-based creation of events calendars via ICS files. 2.2 is the version in smecontribs.
It looks like, from what the wiki contributor suggests, that Sunbird/Lightning will be able to write to Kronolith calendars. However, Outlook 2003 has no support for web-based calendars, while from what Microsoft says on Office Online, Outlook 2007 provides read-only support.