This was my talk. Thanks for posting it! Happy to answer questions.
To try out Sourcegraph, sign up at https://sourcegraph.com and it'll take you on the tour.
Also, I'll shamelessly plug our Chrome extension, which "Sourcegraphifies" GitHub (adding jump-to-def and cross-references): https://chrome.google.com/webstore/detail/sourcegraph-for-gi.... It's the #1 Chrome extension for GitHub.
Finally, check out https://sourcegraph.com/beta to get early access to some new languages and super neat features we're adding soon.