Palmsource, the company
, is skating on the thin ice of financial viability: $30M in cash on hand, $15M in debt, and they lost $15M over the last 12 months. With a burn rate like that, they have to focus on shipping asap using as few resources as possible. If they changed the internals of their software so that it works more like Outlook and less like iCalendar (thus making adapting to the Mac more difficult) and PCs represent the vast majority of their user base, then this is the right decision for them. If they can get Open Source to pick up the slack for them for free, all the better.
Actually, at a measely $224M market cap Apple could just buy them if they thought it was worth it (though I think there are some large shareholders that might fight that).