When I ran a hackintosh. I downloaded the source and managed to compile it for linux.
This was a few years ago mind you.
The main issues were:
1) the linux includes need to be used for mac. Not sure if I used a different include like UNIX or MAC. Can't remember, but if fixed the issues opening the config files and populating the presets. Also helped in making the script files work as windows bat files were not an option.
2) second challenge was the application bundle needed copies of ffmpeg and ffplay to work and they have to be included in the .app bundle. as a quick hack I opened the handbrake app and copied the files to the same path inside the winff compiled app.
It worked, but this was at least 8 years ago. Interestingly enough, winff core app hasn't changed drastically over the years so your main challenge will be on the mac side if Apple has changed something on OSX or if the Lazarus port has a niggle. It might be possible that Lazarus supports the ffmpeg/ffplay dependencies in the project build process, so you'd score there...
I didn't want to maintain an OSX port as both Matt and I don't really want the attention (nagging) of another community. Not very nice of me, I know....
Good luck. I would be interested to know if somebody gets this to work (or just uses Handbrake instead).
Cheers.