GOG store page says it works on Mac.
On a separate note, with all these excuses maybe he’s not wanting to play it as much as you think he does. Or, the man is stuck in his ways and needs to read up on basic computer security. I guarantee Steam is keeping his cc info a lot more secure than his work probably handles his PII.
I tried multiple times, BG1 and 2 are very outdated (imo).