The default license for Depends is the GNU GPL. That means you can freely distribute, modify and distribute modified copies of Depends as long as you include the source code. However, that also means that if you embed Depends in your software, your software has to be licensed under GPL or a GPL-compatible license as well.
In some cases, it may not be possible for you to license your software under the GPL or a GPL-compatible license. Some of such cases include when you're developing Free/Libre Open Source Software (FLOSS) of which the license is incompatible with the GPL. In those cases, I'll be happy to provide a license compatible with yours, as long as it does not infringe on my copyright and insures that the FLOSS version of Depends remains FLOSS.
If you're developing non-free software and want to use Depends in that software, the GPL won't do you any good and I will not provide more leanient open source licenses - at least not without a contribution from your part.
Depends is, therefore, available under a non-FLOSS license, for a fee. The exact amount of the fee will depend on your needs: if you only need to embed the tracker and do not need any help from my part, the price can be quite a bit lower than if you want support over the telephone or want me to come over and develop code for you. Contact me for more information