Ant Commander is free if you use it at home and without relations with any professional activities.
If you want to use Ant Commander for other purposes like at work or in an institution, you must register it. You can find more information about the registration at http://www.antcommander.com/register.html

You may copy or distribute Ant Commander provided that it's a not modified and complete version (as downloaded on the web site).

THIS SOFTWARE IS PROVIDED "AS IS" AND WITHOUT WARRANTIES WHETHER EXPRESSED OR IMPLIED. THE AUTHOR SHALL NOT BE LIABLE FOR ANY DAMAGE RESULTING OF THE USE OF ANT COMMANDER.

It's prohibited to decompile the code.