Hi Alastair,
I'll start with two remarks:
1) for your case, iTunes is not the problem [iTunes is not streaming to your Pinnacle, or you are not using iTunes to access to DAAP server => you should not post in this thread]
2) your iMac cannot be "Intel" and "G5" [it would have been a G5, you would not have any problem]
Indeed, your problem is OS X Lion in which Apple decided to delete Rosetta. Rosetta is part of Snow Leopard and allows the run of PowerPC [code] softwares. PowerPC softwares are made to run with PowerPC chip (G3, G4, G5) but not with Intel chip. If the code of your firefly version is PowerPC only, you cannot run it on OS X Lion.
Now, to "put back to full running order?", you can:
- delete OS X Lion and revert back to Snow Leopard from a backup [Lion is removing more functionalities that it's bringing new]
- replace your Pinacle with a more recent product [look at Logitech, or Airport Express + speakers]
- search for an Intel version of Firefly, it was existing some "svn" (subversion // stability and compatibility are with no guaranty) that might be Intel and PowerPC (Universal)
- if you are not afraid of Terminal and command lines, you can install via MacPorts and run mt-daapd [no GUI = no graphic user interface]
- use virtualization to run under OS X Lion: OS X Snow Leopard, or Windows, or Linux that can run firefly server with a GUI [will slow down your iMac]
- store your music library with an other machine than a computer from Apple [e.g. NAS with mt-daapd/firefly ; can also be a computater with FreeNAS]
- ...
Finally, do not expect any support from a fruit company. Programmers who developed mt-daapd/firefly used reverse-engineering to be compatible with the Apple DAAP protocol [you're out of Apple's €co$y$t€m => no int€r€$t].
To conclude it exists several solutions, but they are not really user-friendly.
Regards.