Make sure your project's public presence (website, github, etc) clearly describes its history and your authorship. Also make sure it disclaims any associations

Make sure your project's public presence (website, github, etc) clearly describes its history and your authorship. Also make sure it disclaims any associations with the team making false claims, either by name ("project X is not created by or affiliated with site Y"), or generically ("project X is not associated with any company or fundraising efforts"). After that, it depends on what you're concerned about. Is it that you think this group is making off with your opportunities? Undermining your own reputation with their false claims – either because they've hidden your achievements, or are falsely implying your endorsement/involvement? Are you worried about more risk if their lies eventually blow up, due to being revealed as deception or failing the in marketplace? Do you simply want to protect third parties who might be conned? No matter what, making sure the real origins and authorship are well-documented in the project's public presence helps you: anyone doing due-diligence is likely to find the truth. Other concerns probably only need formal legal steps if you find yourself crossing-paths with this team in the marketplace, facing quantifiable damages from their falsehoods. Note that it's possible they've been sloppy in attribution and cutting/pasting, but truly have made proprietary additions/improvements representing new IP, and intend to operate a real business. (The email-relayed info may have morphed somewhat in the retelling.) On the other hand, sometimes people run total scams where they carbon-copy an entire website to create the false impression of competence, to raise money for immediate theft. If that's the situation, what you publish and say now could someday prove important in a civil or criminal case against the fraudsters. You'll want to make it very clear you're not coordinating with them in any way.