IOS-RTFKit is a project mainly written in OBJECTIVE-C and C++, based on the GPL-3.0 license.
RTF (Rich Text Format) Parser for iPhone 3.2 NSAttributedString and Core Text
I'm not going to work on this project any more at the moment since OmniGroup has released their RTF parser which is way better than what I'm doing here.
Go check it out:
http://github.com/omnigroup/OmniGroup/tree/master/Frameworks/OmniUI/iPad/RTF/