The summit is interesting because it is unusual* - open source events are usually open access too. The agenda is wide open and is roughly focused on standardization and the future, whatever that is. The invitees are the core developers of all the implementations of Python: regular Python (aka "CPython"), Jython (Java), and IronPython (C#).
I'm not sure what the purpose of the invites is, other than to convey weight. To make the list is to ask "who are the 50 people on the planet who would actually want to come?" Griefers and trolls ("trouble makers" to you) would be bounced regardless so perhaps the invitations are meant to discourage the well meaning but clueless. Every convention has at least a few of those.
* It is not without precedent. See the the Reykjavik sprint.