Thrive is currently not available for Macs due to there not being any programmers on the team who have a Mac.
If you know someone who could make Mac releases of Thrive, please send them our way.
It should not be very difficult to make a version of Thrive that works on Macs. All our libraries have been selected to be cross platform. It should take less than a month for a somewhat dedicated developer to make the mac version happen. Though, they will need to stick around for future releases to also have mac versions.
The current developers don't have the hardware. So what if we got the hardware? It would cost quite a bit of money. The cheapest mac hosting that is perhaps usable is 25 dollars a month (the next tier of hardware is around 40 dollars a month). Buying the cheapest Mac mini would cost around 900 dollars.
Apparently Apple also now charges a yearly fee to register as a developer, which is required in order to have Apple sign any binaries you compile, otherwise others can't run them.