You can find our latest release of Dungeon Builder (v. 1.1 Preview #3) below.
Dungeon Builder for Linux
Dungeon Builder for Mac
If you're having problems downloading Dungeon Builder from the links above, you can find the files on Dropbox as well.
If you're just looking to give Dungeon Builder a try, download the latest version above and write demo as the username and password. Your features and map sizes will be limited, but you should still be able to get a good feel for the application.