iTextSharp is no longer licensed under the MIT/LGPL license. Versions greater than 4.1.6 are licensed under the Affero GPL, meaning you can't even use it in a SaaS (Software as a Service) scenario without licensing your code under the GPL, or a GPL-compatible license.
Other opensource PDF implementations in native .NET include
- PDF Clown (make sure you get the patches to the latest version)
- PDFSharp
- PDFJet open source edition (commercial version also available, and you will need the JDK installed to build this)
There's also a couple of Java PDF libraries (like PDFBox) you can convert to .NET using IKVM.
