Or more specifically, it is Movable Type 4 which is going open source. Currently you can download the beta version of this software for evaluation purposes. I used to have MT powering my blog, back in the days when MT was given away for free. When it became too spammy to tolerate, I switched to WordPress and have been with WP ever since. I doubt that I would be switching back to MT as WP has not only features and plugins to bend it to your will, but great support and a wide variety of themes to choose from.
Seriously, who in their right mind would want to switch away from WP anyway?