The demo is now available, you can grab it from here:http://www.aleajactaest-game.com/What you get in the demo:
12 turns of the Year of the Four Emperors, all side playable
Limitations of the demo:
You can't play past the twelfth turn (in full AGE games, you can always continue past end date)
National morale can't go below 90
Replacements chits can fill up elements but can't create new ones
You can't load an old game (the 12 turns must be played within the same session)
Aside these restrictions, which should not be a big problem within the context of the demo, all features are activated.
On a technical note, if the demo runs, then the full game works, if you are unsure of your configuration or driver compatibility issues.