Postfix. I will not use DJB's software programs for this (or any other, for that matter) project. His license scheme is non-existent, and his idea of where stuff goes and how it interacts with the rest of a unix system is crack-induced. Therefore, qmail is out. I have not had positive experience with Exim, and it does not seem to have any features lacking in Postfix, that I would want for this project. Anyone who knows differently is welcome, of course, to let me know via email or the project forum. Sendmail would work, but I have more faith in my ability to get Postfix working quickly.
TWIG. The alternative to TWIG would probably be phpGroupWare ( here). TWIG has done enough to annoy me in the past that it is not set in stone. However, phpGroupWare seems to be targeted at a similar end to this project. While I wish to use current, off-the-shelf apps, phpGroupWare seems to be rewriting them to conform to its API. It may be that this project ends up just writing applications for the phpGroupWare API.
Scoop. "This is my project, and we're going to use software I like". Basically, I detest Slash. I don't know of other possibly suitable weblog software (besides maybe phpSlash), and I feel Scoop's layout is consistent with a good integrated "feel". I might be wrong, and welcome criticism on this point.
Webmin. I wish for the total VCProject codebase to be installable as a port on a standard BSD system (which is what I develop on). Knowing that people who want to run virtual communities are not always the cleverest admins in the world, I believe a customized webmin interface would be beneficial for user/account creation, and whatnot. Custom Webmin modules will be needed for virtual user management.
phpBB. I've used other UBB clones, and phpBB seems to be one of the easiest to hack around (search for phpBB on sf.net), and seems to have one of the largest feature sets.