I tried to run Arduino 16 (and other version newer than 10) on 2 old Mac laptops, running OSX39, but got
readlink: command not found
messages in the console.
Indeed, readlink doesn't seem to be present in OSX.3.9 (a find / -name readlink -print) didn't return anything.
Despite this error, I can compile .pde.
I'm doubting anyone tests on Panther(10.3) anymore. I haven't kept any Panther machines around.
Most OSX apps require Tiger(10.4), even if it's not explicitly stated. Tiger will run on pretty much any Mac that runs Panther and has a LOT of improvements.
I think the supported OSes should be clearly stated somewhere on the download page.
There are many reasons to avoid an upgrade. I am very happy with this good old titanium running X.3.9, it runs all the apps I need (maybe not their latest version, like MaxMSP 5), I'm not afraid to work with it in difficult conditions (like under heavy rain or in very dusty places), programming arduinos for sound installations. Using Arduino16 is obviously not a good reason to buy a rather expensive license. And anyway, there isn't much room on my system partition anymore.