TensorFlow – part of the Google brain project – has recently open sourced on GitHub a nice playground for testing and learning the behaviour of deep learning networks, which also can be used following the Apache Licence:
Background: TensorFlow is an open source software library for machine learning. There is a nice video “large scale deep learning” by Jeffrey Dean. TensorFlow is an interface for expressing machine learning algorithms along with an implementation for executing such algorithms on a variety of heterogeneous systems, ranging from smartphones to high-end computer clusters and grids of thousands of computational devices (e.g. GPU). The system has been used for research in various areas of computer science (e.g. speech recognition, computer vision, robotics, information retrieval, natural language processing, geographic information extraction, computational drug discovery). The TensorFlow API and a reference implementation were released as an open-source package under the Apache 2.0 license on 9th November 2015 and is available at www.tensorflow.org
Abadi, M., Agarwal, A., Barham, P., Brevdo, E., Chen, Z., Citro, C., Corrado, G. S., Davis, A., Dean, J. & Devin, M. 2016. TensorFlow: Large-Scale Machine Learning on Heterogeneous Distributed Systems. arXiv preprint arXiv:1603.04467.
It is also discussed on episode 24 of talking machines.