Right mouse button is just one issue. There is many other issues need to be taken under consideration. One big thing is dialog layouts. If dialog is so large that part of it is outside of screen it decreases usability of lot.
Even if you can make technically usable it does not mean that usability is good. For small screen devices application with good usability should be usable with finger. As example acrelling from content pane is much more usable than tiny scrollbars that require usage of stylus.
Maemo Qt port takes care of most of technical issues like style and input method but it can't fix bad or unsuitablenUI design.
I strongly recommend that everyone that ports application to maemo pays some amount of attention to usability and is just not trying to make quick and ugly port.