From iText 5.1.0 on, we're releasing iText as a zip file containing several jars. The most important jars in the zip file are the core itextpdf jar and a jar with interesting extra functionality for special use (embedding rich media, geospatial PDF,...). The other jars contain the source code and the Javadoc information.
Furthermore, we've created two new projects on SourceForge. Aside from the core library, we now also have iText RUPS (formerly part of the iText project) and iText XMLWorker (which is a complete rewrite of the XML and HTML functionality). Each of these projects has its own release cycle and jars.
Also new in iText 5.1 is the "Mavenization"; we've moved from ANT scripts to Maven POMs. iText will now by published in the central Maven repository.
Finally, we've replaced classes such as
ArrayList,... with interfaces such as
List,... in several places. You may have to recompile your own code to make iText 5.1.x work.