The first iCal4j release candidate is now available.
The most notable change in this release is the addition of iTIP validation for Calendars and Components. This may impact any iCalendar objects containing the METHOD property.
Note that I have added relaxed validation (enabled using the RELAXED_VALIDATION Compatibility Hint) where I have noticed samples from other CUAs that don't fully conform to iTIP. You may however find examples that I have not yet catered for, so if you experience a validation issue with iCalendar files generated using other CUAs please let me know via the forums: