The good news: Cinderella 2.0 has been released.
Cinderella, for those unaware, is a dynamic geometry system; its special virtue over other such systems is its use of complex number arithmetic to maintain its configurations robustly. For instance, draw two circles and the line connecting their intersection points, pull the two circles apart, and the line will remain visible in a mathematically consistent location: the intersection points from which it is formed have not become undefined, they have merely become imaginary.
The bad news: they've gone to a purchasing model in which, after a one-time charge, they'll send you a temporary license and promise to keep sending you new licenses after the old ones expire. So, if for some reason the people who make Cinderella vanish from the net, so will your ability to continue using the software you've already paid for.
i've never tried Cinderella... but for this example, if one really wants a line between circles even if the circles are not connected, one can construct it that way... and i think i rather prefer it this way. I'm not sure i'm making sense, but i feel this way actually makes the construction more aware of what he is trying to contruct, or the method choosen among the many ways...
btw, the other day i was informed of http://geometryexpressions.com/index.php which seems to be plane construction but done with symbolic math abilities. I haven't tried it yet. (Mac version coming)
Also, i was informed that the software Theorist, which is a excellent software around late 1990s, later got purchaed by Maple, and now exists on its own again and is making a come back as http://livemath.com/ i haven't tried it neither...
if we ever decide to vanish, we will post an unlimited license before that -- of course, the whole licensing model relies on confidence on both sides.
If anyone is really concerned that he or she needs an unlimited license, just contact us at email@example.com; we will send it to you, but you should take great care that it won't become public.
Ulli (50% of the "people who make Cinderella")