I expect I will not be able to view the livestream of the WWDC main public keynote event.
Has Apple announced any plans for non-attendee viewing of WWDC keynote and events?
To prepare for 2018 WWDC I would recommend three things:
As to why these three avenues were selected last year is that the sessions under developer NDA require authentication with an AppleID. Also, on a technical level - the streaming used the latest QuickTime codecs for presumable efficiency, quality. Also, there would be marketing synergies of potential value to Apple by using their own technology for a high stakes / high pressure / high expectations and in demand public event.
Hopefully this helps people prepare for the 2018 remote viewing of the sessions at this year's developer conference.
As a postscript - the WWDC app is showing the live stream on rebroadcast within hours of the main event completing.