Thanks for writing this up, Simon!
Seeing as I work with the folks at WPMU DEV (who make the Network Theme) I can answer the licensing question… It’s GPL licensed so once you’ve downloaded it you can do as you please within the confines of the GPL, just as you can with WordPress itself.
For me the big takeaway from that session is that there is a desire to use WordPress, given the complexity current systems represent and the amount of time soaked up by even the seemingly simplest of tasks. What’s stopping mass adoption is security and scalability.
You made a valid point about the WordPress.com setup. I can tell you that Edublogs (also owned by Incsub, who I work for) – the biggest Multisite after WP.com – runs off three servers and hundreds of databases.
In the session I mentioned a few plugins they’ve released which have a lot of the functionality so others can do the same. Multi-DB allows you to use up to 4096 databases. Something else that was mentioned was combining sites across a network so I talked briefly about post indexer and global site search which helps to unify all sites under a network – useful for content strategy.
There was also a conversation about branding in the session. Each sub-site in a network can, as you will know, have it’s own theme but it’s possible to use different domains too with multi-domains and domain mapping. I already know of one council using domain mapping.
Hope that doesn’t sound like an advert! As I said in the session, I don’t think many people realise just how powerful WordPress *can* be and those plugins do help to show what’s possible.
Of course if anyone has questions about using WordPress I’d happily answer them.