The story started with this post at the Weekly Standard
But there is a copy of the original file at Archive.org (with an added archive.org header).
The article shows code snippets from two different files from the DataTables project.
The first snippet shows the header for the file DataTables.js, which shows the copyright and license notice for the project. This file is the "primary" source file from the source folder /DataTables-1.9.4/media/src/ which defines DataTables as a plug-in to JQuery. The second snippet is from the DataTables file: DataTables-1.9.1/media/src/core/core.columns.js. This code snippet is not in the file DataTables.js despite the path/filename in the browser address as shown in the article.
The developer(s) responsible for this part of the website pulled a set of code snippets from various files from the DataTables project and decided to name the file DataTables.js. These individual DataTables files do not contain copyright or license notices nor do they contain the summary/version comments found in the Healthcare.gov file shown in the article, but since those comments are in the same format as in the original DataTables.js it seems that the developer(s) copied that “snippet” from DataTables.js and decided to not include the license and copyright information.
Some key lessons from this incident are: