Enhance README with license clarification

[stleary]

Description:
Added text to clarify the meaning of public domain. This is to address #1031

Refactoring:
N/A

Testing done:
N/A

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[stleary]

What problem does this code solve?
Adds text to clarify public domain status of the project. No code was changed.

Does the code still compile with Java6?
n/a

Risks
n/a

Changes to the API?
n/a

Will this require a new release?
n/a

Should the documentation be updated?
readme was updated

Does it break the unit tests?
n/a

Was any code refactored in this commit?
n/a

Review status
APPROVED - by myself

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