Wow this topic went in a direction I didn't expect. I think many people misunderstand SMF's license and the reasoning behind it. Its true, Open Source requires redistribution, and SMF's license allows for redistribution, but requires written permission first. Our primary reason is consistency, and security. You really can't compare SMF to Ubuntu. One is an Operating System and not very portable (unless its on a live CD) the other is a web application.
I wouldn't even go as far to compare SMF to Joomla, but since it was the example brought up and its a web application I'll run with it. Again all we require for distribution is keep the SMF package current(update within one week), keep the footer in place, and keep the initial package unmodified. There are many company's right now with written permission. Look as SMF's security history compared other forum software, I'd love to think we have the best Dev team on the net (& I feel we do) but a big part of keeping your forums safe is keeping them current. There are many hosts out there that have these 2 click install scripts, installing old versions of websoftware. I see people here all the time because some host still has YabbSE as a free install and it hasn't been supported in how long? We feel this is a progressive way of looking at software and in fact I'll go on record to say we've been asked numerous times by other company's for permission to use our license.
As for an OSI License, I would love to talk about that, but as metallica has said, we should split the topic & keep this one on task.