Apple has long maintained control over what apps can run on its platform, and it's been able to squash apps that slip through in the past. That means it's quite possible that Popcorn Time's easy iOS installer won't be around for long — but it's also possible that it'll just find another way through in the future. It's also worth remembering that, because this app hasn't been run through Apple, you're letting an app that hasn't been checked over for security issues access to your computer and iPad. The installer can be downloaded from Popcorn Time's website.
Popcorn Time is also using today's release to celebrate its one year anniversary. If the app wasn't enough, it also made this weird animation featuring popcorn people and movie references: