Yes, but please be aware that many features are still missing and that the world will be reset at the end of each test. You can sign up in the forum now or subscribe to the newsletter to be notified when Early Access starts.
We think that the browser is a very capable gaming platform, available on pretty much every computer and every system in the world. It's the perfect match for the kind of play style we have in mind, allowing people to play from their office or while doing something else without having to download, install and run client software.
There is no official mobile support as of now. Our primary focus lies on desktop browsers for the time being. Optimizations to play the game on tablets as well as companion apps for certain aspects of the game are on our roadmap, though.
Nothing is set in stone yet, but we expect the most commonly used payment methods to be available from day one. This includes but is not limited to PayPal, credit cards and paysafecard. Since we roll out our own payment systems, we can add new payment methods over time.
First and foremost, Properous Universe is a browser-based game. While we do have plans to provide a client software that could be offered on platforms like Steam or the Apple App Store, this is a low priority for us right now.