I saw in another thread on here that Adobe just recently released a new version of their SDK, including support for new features that use the Barnes and Nobles eBookstore.
It's likely that iRex needed that code for their update, since they're partnering with B&N.
Adobe has released an update to the Reader Mobile SDK, the software development kit that enables third-party developers to support PDF, EPUB and Adobe Content Server 4 protected documents on reading devices and in smartphone applications. Version 9.1 delivers improvements in performance and rendering, in addition to supporting password-protected PDF files. It simplifies the workflow for authenticating devices with Adobe Digital Editions. The Enhanced Reader Mobile SDK also supports password-protected EPUB files, including EPUB content sold by the Barnes & Noble eBookstore. For more information, please visit the Reader Mobile Developer Center.