Apple will stream the WWDC 2013 keynote live online. You need though an Apple TV.
The highly anticipated WWDC 2013 keynote will take place today at 10am PDT. MacRumors just discovered that Apple will stream the WWDC 2013 keynote live on the Apple TV. An WWDC 2013 icon has appeared in the channel line-up.
Apple did that also in 2010 for the iPad mini event. There is a chance that Apple will also stream the WWDC 2013 keynote on their website. We still have to wait and see if that will be the case.
The WWDC 2013 keynote will also be streamed online on this page.