Flarum is in it's very early stages and is currently in pre-alpha. It's definitely not pretty, but Toby Zerner the developer of the esoTalk forum software has decided to publish it on Github and make it an Open-source community project since the cancellation of the Kickstarter campaign. 

Everything you need to know is in the README on Github and I'm really looking forward to seeing Flarum make some progress.