Unfortunately, no one in the development team has any experience, not to mention expertise, with the typographic requirements of these RTL scripts. We don't have experience with Indic or CJK scripts either, but at least for Indic, Tamil or Japanese some volunteers showed up to work on support for their writing systems.
Which is to say: If you can find someone who has experience with Hebrew typography and font handling, as well as programming experience (preferably C++), by all means, encourage this person to contact the development team. There is some legacy code available, and cooperating with the external developers who are working on other non-European scripts might not be a bad idea.
As for the coding experience: C++, Qt, font technology, PostScript, text layout. There was an (unfortunately unfinished) project to implement a new text engine using ICU, which is available here: svn://scribus.net/branches/ScribusOIF, [^] which would be a good starting point.
As for ICU see: http://userguide.icu-project.org/layoutengine [^] and http://www.d-type.com/page/text_layout. [^] It may also be helpful to contact the team that is working on Indic language support to avoid double work. See: http://lists.scribus.net/pipermail/scribus/2012-August/047258.html