I have received a Cease and Desist letter claiming that I've engaged in defamation. What should I do?
You should seek the advice of an attoney if you've received a Cease and Desist letter. Your attorney should be able to give you legal advice as to how to proceed with the Cease and Desist letter. Do not contact the person who's served you the Cease and Desist letter.
I see. However, I'm not in a position to seek the advice of an attorney. I received this letter because of code I wrote and published on GitHub. Is there anything else I can do to resolve this issue?
If you are unable to seek the advice of an attorney, you may want to consider taking the following steps:

1. Review the content in question: carefully review the code you wrote and published on GitHub and any related comments or documentation. Make sure you understand the basis for the accusation of defamation.

2. Determine the validity of the claim: assess the merit of the claim made against you. If you believe the claim is false or unfounded, consider providing a response outlining your position on the matter.

3. Consider removing the content: if you determine that the content in question is indeed defamatory, consider removing it from the public domain to avoid further legal action.

4. Engage in communication: if you decide to respond to the Cease and Desist letter, do so in a calm and professional manner. Explain your position and attempt to find a resolution without resorting to legal action.

It's worth noting that while it's possible to handle legal issues without the assistance of an attorney, it's always advisable to seek legal counsel if possible.