update README

Author: jadamcrain

README.md

@@ -1,2 +1,7 @@
 # rodbus-no-serial
-Build of the rodbus library for .NET without serial support
+Builds of the [rodbus](https://github.com/stepfunc/rodbus) library for .NET without serial support.
+
+## License
+
+Refer to [`License.txt`](https://github.com/stepfunc/rodbus/blob/main/LICENSE.txt) for the terms of the non-commercial license.  This software is 
+"source available", but is not "open source". You must purchase a commercial license to use this software for profit.