If a project has no a license or has unknown authors, is it public domain?
Is a project without license public domain?
licensing
As usual, IANAL, consult a lawyer for legal advice. That said:No. The default is all rights reserved. You are not allowed to copy someone else's work without the author's explicit permission, even if the author is unknown.Works are free for you to use under the following circumstances:You have written it yourself, and haven't transferred your rights to anyone else (note that in some jurisdictions, all your intellectual property is automatically transferred to your employer, even if the contract doesn't state this explicitly).The author has explicitly released the work into the public domain. Note that some jurisdictions in the world do not acknowledge this; in those countries, you may still be violating the law (although it is unlikely that the author is going to sue).The copyright holder is a government institution or similar legal person whose works are in the public domain by law.The author has given you explicit permission.The author has released the work under a permissive license (e.g. MIT, Apache, or BSD licenses). You are still bound by that license though.All the authors have been dead for long enough (where long enough means 70 years in many countries, but the figure may differ either way). I doubt you'll see this in the software realm anytime soon, but it's very relevant in arts and music.