The Universal Serial Driver, either direct from Uniden, or of my site have to be downloaded and installed into Windows.
If you are on a MAC then I assume you will running Scan125 on you MAC under with Windows running under bootcamp, parallels or some of the virtual machine setup.
On my site if you go to: http://nick-bailey.co.uk/scan125/download/
then you will find
I'm not a MAC user but I assume in your Browser (Safari) when you click the file you will be offered to download/save the file?
For best support please contact the Email address given on the Scan125 webpage on my website. I only get to look at various forums (other than my own Scan125 forum) on an irregular basis so contacting me directly is always the best option.