I've got a number of software projects, licensed under varying licenses. For simplicity, let's take one of them, licensed under the GPL.Obviously, the GPL requires various things, and there may be occasions where people don't do all those things. If I notice those, I see two choices:Contact the relevant person with notification and request to comply;Turn a blind eye.Fine, that's up to me. However, if someone else contacts me to say that they've found someone who's not complying with the GPL, does anything change? Does their involvement and thus the fact that I am proven to know about the license violation change how I can react? Am I, in this scenario, obliged to enforce my license by contacting the offending party?
Are you obliged to enforce your license?
licensing;gpl;enforcement
GPLThe GPL license doesn't have any specific requirements to make you enforce the license and the copyright holder is the only person who can take any action.The copyright holder is the one who is legally authorized to take  action to enforce the license.(Violations of the GNU Licenses - GNU.ORG)Copyright LawSo only something in base copyright law could cause you to lose your rights from non-enforcement. Short answer: No, you won't lose your copyright if you do not defend it. That is something that applies to a trademark.In the United States, if a trademark owner stops using a mark without  intending to resume using it in the future, the mark will be deemed  abandoned. Under U.S. trademark law, non-use of a trademark for three  consecutive years creates a rebuttable presumption of abandonment of  the mark (whether or not it is registered). Temporary or seasonal  non-use of a trademark, particularly when such cyclical use is typical  in an industry or market, generally does not constitute grounds for  abandonment under U.S. law. Rather, periods of non-use must be  accompanied by the intent not to resume use.In many other countries, grounds for abandonment depend solely on  whether the mark at issue has been in use, without regard to the  trademark owners intent. The period of non-use required to show  abandonment of a mark typically ranges from three years (e.g., in  Australia, Japan, South Korea, Canada, China, Russia and many Latin  American countries) to five years (e.g., in various European  countries, such as Ireland and Norway).(Fact Sheet: Protecting a Trademark - International Trademark Association). Laches defenseAnother reason you may be unable to defend your IP rights after a long period of not enforcing it is what is called a laches defense. This is when there has been an unreasonable amount of time in pursing a claim. Laches is an affirmative defense and must be brought forth and proven by the defendant. The US Supreme court has stated that laches does not bar copyright infringement claims (Petrella vs MGM).The majority rejected those arguments, however, saying copyright law  was clear in allowing lawsuits up to three years after an infringing  act, setting up a rolling period for owners like Petrella to sue  although they can only collect on profits earned during that  three-year window.There is nothing untoward about waiting to see if an infringers  investment paid off, Ginsburg wrote. In fact, the law  allows a  copyright owner to defer suit until she can estimate whether  litigation is worth the candle.The Supreme Courts decision brings certainty to this issue, which  was unique in the Ninth Circuit, said William Kane(Unusual Split As Supreme Court Upholds `Raging Bull' Suit Vs. MGM - Forbes)So there isn't anything different with someone telling you that someone has infringed on your copyright. You aren't required to enforce it. You can probably even wait and decide later that you want to enforce it but you can only do that within three years of the last infringing act and you can only expect damages based upon the last three years.More useful info about copyright myths (including this): http://www.templetons.com/brad/copymyths.htmlI Am Not A Lawyer... if you want real legal advice you should contact one.