If you can't find anyone who has one and is willing to test, I *do* have an old one, but there's a reasonably high chance that it's much too old, especially considering Apple's record regarding backwards compatibility (for reference, I believe it's on Snow Leopard). Feel free to reach out if you want me to try anyway, but definitely wait at least a week for other people to respond. Because it's so old that compatibility for the relevant software could very feasibly be a major issue, I will not try to set it up unless you explicitly ask me specifically to try it.
That said, my hunch is that it's probably an Allegro bug, though I am aware of at least one way to make an Allegro application that runs properly in Linux but not Windows (but still compiles on both), so it's not infeasible that there could be another mac-related issue. I once made something on my Linux machine while my Windows one was broken (hardware issue), and once I got the parts to get the Windows one working again, it turned out the Windows version didn't work because there was a missing addon init function call (I think it was al_init_primitives_addon). On Linux it didn't matter, at least not for what I was doing, but on Windows it turned out to be important. I doubt it's what's happening here, but I can produce a minimal example of it if you want (and/or possibly look for other combinations with similar effects). In any case, while I highly doubt one of them could have been missing this long without getting noticed, it could be worth double checking, since the library doesn't seem to define what should happen if you try to use things without calling those initialization functions first.
