This software is free for all (e.g. personal, academic, non-profit, non-commercial, government, commercial, etc) to use.
Please cite using: Yap CW (2011). PaDEL-Descriptor: An open source software to calculate molecular descriptors and fingerprints. Journal of Computational Chemistry. 32 (7): 1466-1474
Download the source code here. The source code is released as public domain. However, any part of the code that uses CDK, AMBIT2, RapidMiner, Apache Commons CLI, and l2fprod will still be restricted by the respective licenses.