Adding license info to the top level README file too.

diff --git a/README.md b/README.md
index 4c4d1ae4892ca33e4b5a26eb99c6208a85ac1a90..a12779de2d2e2e590e662fd148de687d60dc7478 100644 (file)
--- a/README.md
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@@ -1,3 +1,5 @@
 SymbiYosys (sby) is a front-end driver program for [Yosys](http://www.clifford.at/yosys)-based formal hardware verification flows. See [http://symbiyosys.readthedocs.io/](http://symbiyosys.readthedocs.io/) for documentation on how to use SymbiYosys.
 
 Many example designs using SymbiYosys have been published on the [ZipCPU blog](http://zipcpu.com).  Please consider browsing the [formal verification page](http://zipcpu.com/formal/formal.html) of the [ZipCPU blog](http://zipcpu.com) for examples and commentary.
+
+SymbiYosys (sby) itself is licensed under the ISC license, note that the solvers and other components used by SymbiYosys come with their own license terms. There is some more details in the ["Selecting the right engine" section of the documentation](https://symbiyosys.readthedocs.io/en/latest/quickstart.html#selecting-the-right-engine).