Trademark Dispute: open source code in commercial product

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Illustrative scenario prepared by my practice.
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Hypothetical question

English isn't my first language so bear with me. Has anyone dealt with something like this? I'm not sure what my options are.

open source code in commercial product. I've been dealing with this for about 11 months now and the situation isn't improving.

This involves software/code I developed over the past 10 months. I do not have documentation proving my ownership and timeline.

What are my legal options here? Is it worth pursuing?