Chromaprint's own source code is licensed under the MIT license, but we include some parts of the FFmpeg library, which is licensed under the LGPL 2.1 license.
As a whole, Chromaprint should be therefore considered to be licensed under the LGPL 2.1 license. We are hoping to remove the included FFmpeg code and make MIT the only license used in the project.
Note that when distributing Chromaprint in binary form, you should also take into consideration the license of the external FFT library that you compile Chromaprint with.
Copyright (C) 2010-2016 Lukas Lalinsky
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
GNU Lesser General Public License version 2.1 (LGPL 2.1)
You can find the full text of the license here.