From the blog "Leadwerks Company Blog"

Ultra App Kit 1.1 is now available on our website and on Steam. This free update brings cross-platform development to our fast resolution-independent GUI toolkit. To download the new installers, click on your account purchases. In addition to Windows, Mac and Linux are now supported, which means you can code once and compile everywhere to easily create cross-platform GUI applications. Builds on Linux use minimal dependencies and will work on virtually any distro without any additional