The license text is currently included in many files, but some of them remain unlicensed.
Examples:
Makefile
VS project files (in this case it can be presumed to be in the public domain because they were generated by the program).
The README file is licensed under the simh (MIT) license, but some items may not be licensed under it.
Solution

• Add the license file in the root directory. It can look like:

1. All our contributions are freely available for use, copying, distribution in their original and modified form, but without any warranty.
2. All Makefiles and documentation files are licensed under the license describes in the source code of the program.
3. Third party programs may be licensed in their own right, but section 2 applies to them.

(This problem also applies to simtools. I opened a report there because some files have a strange license other than the one here).