FDTD++ can be downloaded below, simply by registering.
Register and Download FDTD++
FDTD++ is distributed under the Algorithms in Motion LLC license (v1 or later), which is similar to the GNU GPL1, and can be downloaded by using the form to the right. This will register you to the FDTD++ Newsletter (updates, news, etc.), and you will receive a welcome email with the username and password.