Our $40k goal is only with Windows PCs in mind, but we absolutely would like to. The game is currently programmed in C#, but Jonathan and I have been looking into solutions that would allow us to put ATG on other platforms. Stay tuned!
We don't know what all of the different ways you'll be able to download ATG are yet, but by contributing to the Kickstarter campaign at the very least you'll be able to download the game directly from our website 100% DRM-free, no strings attached.
I'm afraid that ATG will be single-player only. We'd really like to add MP to our games, but it really is a huge amount of work and our current schedule and budget are pretty limited. However, if ATG pans out or we go way beyond our finding goal we're definitely considering it for this or future projects!
ATG will be released only in English, but if we're able to hit our $70,000 stretch goal it will be possible for the community to mod the game into any language!