The problem is actually not so much running on OSX, which works, but that nobody has yet created a good package. I'm not myself familiar with packaging for OSX so I can't say for sure what's holding it up. I just know that so far there have been problems when people tried.
Calligra is an application suite with some applications that are office applications and some that aren't. Krita, for instance, is not an office application, it's a paint application for professional artists. In fact, before Krita created its own website (krita.org) the spread of it was hampered by its association to the office applications.
Btw, the Calligra Active group, who is working on the tablet edition of Calligra, have started to create QML components of the word processor, spreadsheet and presentation modules. For those you who are not into Qt and QML development, this means that you will be able to embed, say, a spreadsheet into your application by just adding an include file. This is the power of Qt.
Here is the short story on the Calligra Suite:
Calligra was indeed spun off from KOffice about a year ago. Some call it a fork but it was actually more of a split. Some applications moved to Calligra (KPlatoPlan, Kexi, Brainstorm, KPresenterStage), some others were indeed forked ( KWordWords). Many of them got new names as did the whole suite (which you can see in the previous sentence).
KOffice was a nice enough office suite for users with simple needs, but the Calligra team has bigger plans. One of the big strengths oof Calligra is that it's both very modular and the UI is well separated from what we call the Office Engine which handles loading, storing, saving, and rendering of documents but not editing. This is the result of the work from the last 2 years, much of it sponsored by Nokia. During the same time the engine itself has also been much improved with a completely new text layout engine, automatic tests to ensure that we don't get any regressions, many new features and improved stability. There is a company called KO GmbH that does commercial work on Calligra, and they have had most of their business around the engine and the import filters for Microsoft formats.
So during this last year much much energy has been put into the office engine which benefits all platforms / UI's and a number of new UI's have been developed: Nokia Harmattan Office for the N9, Calligra Mobile for the nokia n900 (this one is actually a bit older), Calligra Active for the Plasma Active environment which just got announced will be used in the Spark tablet.
What has indeed been lagging behind was the desktop UI which would give you the impression that you got. But the last few months we have also seen a lot of work here. The style manager has been improved, the text formatting dialogs (actually dockers in the case of Calligra desktop) are much nicer now and new features like footnotes/endnotes and many others have been developed and integrated. Note that these features were already present in the engine so it was a relatively minor effort to implement them in the UI. Also other applications than the word processor have gotten a number of new features but Calligra is so modular that it's sometimes difficult to say which application benefits the most from a new feature. If it's available in one application it's also available in the others provided that the feature makes sense in them.
Now we are getting closer to the first release. We hope it will be at the beginning of March, and we have great hopes that people will like what we have done.