Truecrypt is free and opensource, but it can't crypt the system partition etc.
I'm using DCPP for more than 2 years, and i'm very satisfied with it.
If you have a 200gb partition, you can encrypt/decrypt while you are working on it! Encryption doesn't format the disk like TC, and others.
And yes, dT keygen for DCPP 3.0 doesn't work.