Add an MIT license to the repo to prep for open release

LICENSE.txt

@@ -0,0 +1,8 @@
+Copyright (c) 2019-2023 Massachusetts Institute of Technology
+Author: Abraham Levitan, abraham.levitan@psi.ch
+
+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.

README.md

@@ -29,6 +29,6 @@ plt.show()
 Full installation instructions and documentation can be found [here](https://cdtools-developers.github.io/cdtools-docs/).
 
 
-CDTools was developed in the [photon scattering lab](https://scattering.mit.edu/) at MIT, and further development took place within the [computational x-ray imaging group](https://www.psi.ch/en/cxi) at PSI. If you would like to publish any work that uses CDTools, please contact [Abe Levitan](mailto:abraham.levitan@psi.ch).
+CDTools was developed in the [photon scattering lab](https://scattering.mit.edu/) at MIT, and further development took place within the [computational x-ray imaging group](https://www.psi.ch/en/cxi) at PSI. The code is distributed under an MIT (a.k.a. Expat) license. If you would like to publish any work that uses CDTools, please contact [Abe Levitan](mailto:abraham.levitan@psi.ch).
 
 Have a wonderful day!

docs/source/intro.rst

@@ -7,7 +7,7 @@ Introduction to CDTools
    Introduction to CDTools
    -----------------------
 
-CDTools is a python library for ptychography and CDI reconstructions, using an automatic differentiation based approach.
+CDTools is an open source python library for ptychography and CDI reconstructions, using an automatic differentiation based approach. It is distributed under an MIT (a.k.a. Expat) license.
 
 .. code-block:: python