A full transcript of the interview can be found at: txt / html / pdf.

Kutta gave a clarification on the SDK question after the interview:

The Portal 2 Authoring Tools were released in beta form a few weeks back. We anticipate a non-beta release soon which includes some useful fixes. As I mentioned in the interview, there are currently no plans to release the source code for total conversions at this time since the authoring tools allow you to create a huge variety of maps and gameplay experiences without creating any new entity types. So, if by “Portal 2 SDK” you mean the authoring tools, then those are already out in beta form and will come out in non-beta form soon.

Here’s the blog post where we released the tools:

http://www.thinkwithportals.com/blog.php?id=5443