I just heard about a new service starting up called
Greenhouse Interactive. Basically it looks to be a Steam-like system with a focus on independent games, however rather than being Windows-only as Steam is Greenhouse is available for Windows, Mac and Linux and allows you to download games for any platform after purchasing them (provided a port exists, of course.) Basically, if Aquaria were available through this service I'd be able to purchase the Windows version now and upgrade to the Linux version when it's available without having to buy the game a second time, which would be quite nice.
Are there any plans to make Aquaria available through this service?