Any plans on Blue Iris coming to MacOS or Synology Diskstations?

You would have to email support. Highly unlikely for mac and never for synology. It would be silly to waste money on a mac when windows machines are so cheap and readily available. Most setups can run on a 100 dollar system, see wiki.
 
I'd be interested in a linux based version. Been a Windows user for decades, but have been migrating to linux more and more of late.

There's nothing wrong with the Windows version of BI.

How can you tell if someone is a mac or linux user? Don't worry, they'll tell you.
 
I'd be interested in a linux based version. Been a Windows user for decades, but have been migrating to linux more and more of late.

Search using google, there are some out there for the MAC, but don't know how they match up (SecuritySpy, Sitehound, etc) with Blue Iris. Synology has Surveillance Station. I"m a Linux user, was using BlueCherryDVR, but support was lacking, as I waited 6 months for them to look at my cam that didn't work with BC and finally switched to Windows and Blue Iris.
 
There's a program called "Crossover" which can run Blue Iris on a Mac or Linux, with some shortcomings. Besides it being totally unsupported by the developer, I think BI has trouble enumerating network interfaces so you might have trouble with the web server (iOS and Android apps and UI3 web interface). It probably will also not be able to use any kind of hardware acceleration, and may not be able to play mp4 files even though it can probably create them.

You're far better off buying a cheap used small form factor windows PC. There's a post in the wiki about choosing hardware for Blue Iris.