I have changed the (private) product download page for paying customers to let you download The Polynomial for any operating system regardless of which operating system you bought it for originally. You may have bought it for Windows, and now you can play it native on Linux or OS X without buying it the second time.
Also, I'm currently working on experimental pay-what-you-want sale! The minimum price is $3 (any lower and I would feel you are supporting payment processing companies too much, which are not the cause that you'd want to donate your money to, I suppose)
The scripts are ready but I am still working on the design.
You can just buy it through this blog post for now:
The price is in USD , without VAT, and minimum is $2.99.
(to be honest i'm really curious if anyone will buy it through blog post before i work on all that fancy design for sales page)