Just to let you know, I decided to work on inkscape.org website again from scratch, this time using Drupal 7, with reworked base theme, design and structure. The plan is to integrate all sections (news, docs, forum, planet) so that they have unified look & feel and could be accessed using the same user account.
Regarding forum, I would prefer built-in drupal module - it's clean, slick and highly integrated with core. Here is sample how it could be themed: http://dc2009.drupalcon.org/forum (btw, that website appears to be designed in Inkscape).
Trying to recreate exact MediaWiki behavior in Drupal is going to be tricky. Maybe we should just decide either to stay with MediaWiki or do it the Drupal way? Inkscape wiki is very poorly structured, e.g. it combines end-user documentation with developer discussions, private notes with release notes. If we were moving it to Drupal it would be best to make the migration manually, split content into separate content types with different permissions (currently anybody can edit roadmap or release notes!) and clean it up by removing any outdated information or spam.
Stable version of Drupal 7 will be released at the beginning of 2010. What should we do meanwhile? - implement at least homepage using Drupal 6 and one of the themes we have so far: (http://drupalready.com/playground/inkscape.org/news and http://inkscape.org/drupal/ ) - or leave inkscape.org as it is and focus entirely on Drupal 7?
I opt for second option as I don't like any of the current themes.