For the lawyers, we should point out that the things here do have licenses, and so aren't entirely free. We just mean the licenses are relatively unrestrictive.
In our products, we use:
The Rapture3D Ambisonic Player uses libsndfile which is written by Erik de Castro Lopo and licensed under the LGPL. It's a really useful C library for reading and writing soundfiles. It's available from http://www.mega-nerd.com/libsndfile/.
Most of the Blue Ripple Sound graphical user interface components have been written using wxWidgets. This is a cross-platform C++ GUI toolkit which is written by Julian Smart and others and is licensed under a variant of the LGPL. It is available from http://wxwidgets.org.
Some versions of Rapture3D use the PortAudio Portable Real-Time Audio Library, which is Copyright 1999-2008 Ross Bencina, Phil Burk and others. See http://www.portaudio.com.
We use the following HRTF data. Note that we process the data quite heavily, so don't blame the folk below if things don't work for you!
To give something back, here's a simple Windows UHJ stereo to Ambisonic B-Format conversion tool for Windows. It converts stereo material that is in the UHJ format (typically from Nimbus Records) into Ambisonic B-Format (using just the WXY channels). It uses the "naive" speaker-agnostic approach to this.
To download, click here. Read the license before installing.
Blue Ripple Sound Limited is a leading specialist in Spatial Audio technology.
We draw on years of experience with Higher Order Ambisonics and high performance programming.
We're based in Central London and can be contacted at firstname.lastname@example.org.