A: Yes, absolutely!  Once you've bought the game, you've bought the game, not an installation of the game.   If you log in with the same login credentials on any device you will have the benefits of your purchased license.

A: Simple economics.  We want you to enjoy the game and we want you to get a chance to play it, but all of the work that went into the game cost time and money to make.   We are offering it for, we feel, a very reasonable and competative price, but we need to have money coming in if we want to have more games coming out.   And we do have plans for more games!

A: It won't be in the long term.  We fully intend to release it for iOs and Android Tablets.    And we had a choice, we could release it now with just Windows, Mac, and Linux, or we could hold off sharing it with folks and release everything together.  We chose to make it available sooner even on a more limited range of platforms.