I bought FLIRC specifically to use with Kodi on a new iMac without an IR receiver. (There is a picture of this remote on the website, so it seemed reasonable to expect it to work.) But there is no controller map for this remote, and it seems impossible to duplicate the behaviour of the original so that, e.g., the up arrows work for navigation, but also change volume while a file is playing. Have i wasted my money?

No, I'm working on remotebuddy integration soon and this feature will be possible. It is currently not something that's possible at the moment. I'm really sorry about that. I think something will come by the end of this year.  I was unaware that the apple remote had that functionality. If I had known, I would have done something much sooner.