The silx toolkit is a software library and one of its goals is not to impose any license to the end user.
Silx follows the permissive MIT license although it may include contributions following other licenses not interfering with the previous goal. Detailed information can be found in the copyright file.
Silx uses the Qt library for its graphical user interfaces.
A word of caution is to be provided.
If users develop and distribute software using modules accessing Qt by means of Riverbank Computing Qt bindings PyQt4 or PyQt5, those users will be conditioned by the license of their PyQt4/5 software (GPL or commercial).
If the end user does not own a commercial license of PyQt4 or PyQt5 and wishes to be free of any distribution condition, (s)he should be able to use PySide because it uses the LGPL license.
The MIT license follows:
Copyright (c) European Synchrotron Radiation Facility (ESRF)
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.