Darwinports is a download/update manager for Unix tools on Darwin, so the fact there's a Darwinports version means it's been ported to Darwin and should run on your system. Ocrad is GNU-licensed freeware. Darwinports is also freeware, but is probably a different license, and it'll require installation before you can use the instructions to install Ocrad via Darwinports.
I'd be interested also. I don't know of any freeware/opensource OCR, but I do know of a source that is not really 'free'. I got mine bundled with my scanner. It is an old model, drivers (and OCR) are OS9. So, when it finally dies, or I can no longer run Classic, I'll be in the market for a new one, and I want to make sure it comes bundled with OCR, or find a good opensource version.
Ahhh, a bit of googling, here's 2 - but no reviews...
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