You pose a very interesting question, @molona.
It is difficult to avoid the web as a resource so, I would venture to say there is no such thing as a developer who is NOT (in some form) a web developer.
My experience with events like this in the past (and only as a participant - this is my first time facilitating and I have NEVER attended a Code Retreat*) is primarily Web Developers and many Mobile Developers. The platforms/technologies I have seen most often are Ruby on Rails, iOS, PHP, jQuery; pretty much everything Sitepoint is currently selling a book about!
*It was serendipity for me.
I was very interested in attending a Code Retreat when I discovered it (mentioned on a Podcast). It was a disappointment to discover that, among the GLOBAL day of Code Retreat
, a big city like Orlando was not represented. As a matter of fact, at the time there was only ONE in all of Florida (in Tampa). So, having attended numerous tech events in the past I felt it time to "give back" and volunteered to make it happen in Orlando.
When I learned a bit more about the structure of the day and responsibilities of the facilitator it appeared to be very similar to proctoring a training class; which is what I do as part of my full time job - teaching Software Developers!
I am now looking forward to the day and, although a bit disappointed I cannot be a participant, excited for the chance to help make the Global Day of Code Retreat