At the moment, the rule in the Ninth Circuit (which includes California) is that the 3 year statute of limitations for a copyright infringement claim begins when the plaintiff "has knowledge of a violation or is chargeable with such knowledge." Polar Bear Productions, Inc. v. Timex Corp., 384 F.3d 700 (9th Cir. 2004).
This rule is very susceptible to be discarded, however, in light of TRW, Inc. v. Andrews, 534 U.S. 19 (2001) which is very critical of starting any statute of limitations clock based on the "discovery" date of the wrong -- instead of the date when the wrong actually began.
If the question of when the clock starts for a copyright infringement claim is ever put squarely before the Ninth Circuit in light of the TRW case, I think it quite likely that current discovery rule will fall. See Auscape International v. National Geographic Society, 71 USPQ2d 1874 (S.D.N.Y. Aug. 12, 2004) for a well reasoned analysis that concludes that the copyright statute of limitation begins when the infringement first occurs.
At the moment, however, the controlling rule in the Ninth Circuit is that the statute of limitations begins when the plaintiff "discovered" the infringement.
As for what you should do about the apparent infringement, please consider carefully what damages you allegedly suffered. You'll need to articulate your "actual" damages. You can, of course, rely on the statutory damages offered by the copyright statute but the quantification of those damages is wholly up to the judge. Also, don't forget that you cannot enforce a copyright unless the copyright is registered with the Copyright Office.
This is a great question, because there really is no bright line answer.
Section 507(b) requires that all civil actions under Title 17 be commenced within three years after the claim accrues. However the term “accrual” is not defined.
Generally, the Supreme Court has held that accrual occurs when the plaintiff has a present cause of action, that is, when “the plaintiff can file suit and obtain relief.” For torts, and copyright infringement is a tort , the traditional rule is that “the tort cause of action accrues and the statute of limitations commences to run, when the wrongful act or omission results in damages." Under this approach, accrual means the point at which plaintiff has a cognizable claim, i.e., the date on which the violation of an exclusive right occurs.
But, “accrual” could also mean the point at which plaintiff is aware of facts supporting a cognizable claim or should have been aware of those facts, i.e., when plaintiff is deemed to have “discovered” the violation. This was the case in Armstrong v. Virgin Records.
Disclaimer: The above material is for informational purposes only and should not be considered legal advice, and does not create an attorney client relationship.
You have received some great advice; I only want to add that if you want to act you should find an attorney who is well-versed in copyright law to assist you as soon as possible.
Notice: The below is for educational and informational purposes only, is not a reflection on or a representation of any views or opinions held by my employer, and should not be construed as legal advice. Nothing herein is meant to create an attorney-client relationship.
You received some good advice from the other posters. I would only add that, with respect to statutory damages, you are only elligible if your copyrighted work was already registered at the time of infringement. If you wish to pursue a potential claim and do not have a copyright registration, you will need to obtain one first and rely on your actual damages, as aptly explained by Mr. Ballard.