There indeed is a utility class for removing such layers in the iText Xtra package (not the extrajars, but itext-xtra.jar): com.itextpdf.text.pdf.ocg.OCGRemover which makes use of the class OCGParser in the same package.
There are a few ways to getting to know that you used itext, fe. define tags in pdf which will be generated by itext. But most of all: if you are running into commercial softwareprojects you are also running into commercial-/software law-situations. It is not very hard to be forced to a source check by a independent company (which will be specialized in source-analysis).
iText is a PDF library for Java which was originally developed by Bruno Lowagie. You can still see that in the old versions of iText (prior to 5.0.0), the packages are called com.lowagie.* Some years ago, Bruno Lowagie founded a company around his iText product, iText Software. At the time the domain name itext.com was not available, so he registered itextpdf.com. Starting from version 5.0.0, the package names were renamed from com.lowagie.* to com.itextpdf.*. It is a common practice to name your packages after the reverse of your domain name.
Library to create and manipulate PDF documents in Java and C#. Use this tag for code using iText versions up to 5.5.x. For iText versions from 7.0.0 onwards a separate tag "itext7" is available. Remember to also add the tag for the language you're using.