We're planning on updating the demo here and on Steam with all the changes we made over the past couple of years. It will be mostly about small adjustments, don't expect big content changes!
The alpha will be made available through Steam (because it has this feature builtin) or through email if someone is interested in providing detailed feedback but doesn't want to install Steam. We will, however, restrict the number of players simply because we won't have time to go through all the feedback if we send it to too many people.
In any case, you're free to join the alpha! We'll make a post about it either this weekend or in the next with the details.
I'm sorry for our slow pace, but it has been hard to cope with our day jobs and personal issues. We're still on it though! The alpha will soon be available and we hope to have the final release early next year.