"How will 'watch parties' work?"
Taken from Backer Update #15:
Each guest attending a watch party will need to have their own access to whatever episode(s) you want to watch together. That means that – unfortunately – you won't be able to let all of your friends watch an episode that you own or rented for free.
We wish we could give you the option to share your episodes with friends remotely and for free, but there are a lot of technical, legal and financial reasons we're not able to. Instead, we're working on a system to allow inexpensive "Day Passes" – probably $0.99 each – so that your guests can rent the episode just long enough to participate!