Unity 5 game engine on Ubuntu linux (native)
Unity 5.1 Game Editor running on Ubuntu 15.10 linux (native)
http://blogs.unity3d.com/2015/08/26/unity-comes-to-linux-experimental-build-now-available/
System Requirements
64-bit Ubuntu 12.04 or newer (just like our player, the editor will run on most βmodernβ 64-bit Linux distributions, but official support is only provided for 64-bit Ubuntu 12.04 or newer)
Unity is a cross-platform game engine developed by Unity Technologies and used to develop video games for PC, consoles, mobile devices and websites.
Unity Pro is available for a fee and Unity Personal has no fee; it is available for any use to individuals or companies with less than US$100,000 of annual gross revenue.On March 3, 2015 with the release of Unity 5.0, Unity Technologies made the complete engine available for free including all features, less source code and premium support. Unity is noted for an ability to target games to multiple platforms.