Fix some headers & license reference

[skrawcz]

Fixes some issues from RC release.

Changes

• removes license file reference because it's in the contrib license file
• adds more headers

How I tested this

Notes

Checklist

• PR has an informative and human-readable title (this will be pulled into the release notes)
• Changes are limited to a single goal (no scope creep)
• Code passed the pre-commit check & code is left cleaner/nicer than when first encountered.
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output)
• Placeholder code is flagged / future TODOs are captured in comments
• Project documentation has been updated if adding/changing functionality.

[skrawcz]

this will be included in the apache-hamilton-contrib release LICENSE which lives under that module.

[jernejfrank]

👍