This small changes are minnor builds. They are free updates for fixing bugs.
New version comes every several months and has a lot of new features. It’s better for the users to be able to use their old version lifelong instead of enforcing subscription models like most companies does. And since this is giveaway not sure it’s free so no need to pay for anything
There is version for Linux, but not sure if it would work this is why it’s not included in the giveaway
https://iristech.co/download/3334/
The giveaway code should work for it also