Swift is a open-source programming language for iOS, macOS, Linux, watchOS, and tvOS apps that builds on the best of C and Objective-C, without the constraints of C compatibility. Swift adopts safe programming patterns and adds modern features to make programming easier, more flexible, and more fun. Swift’s clean slate, backed by the mature and much-loved Cocoa and Cocoa Touch frameworks, is an opportunity to reimagine how software development works.
If you’re interested in coding along during the meetup, check out this tutorial to get set up.
And here is the official Swift download page that includes binaries for some Ubuntu distributions.