Sorry, Development (IDF) only is available on Windows.
Deployment (runtime) is available on many platforms.
See the Platform Availability Matrix on Frontline.
http://frontline.compuware.com/products/uf/tech/15617.aspx

You might be able to use a windows emulator layer on Linux. I know of at least one 'at home' Uniface person who does this using Wine. But the Uniface GUI isn't available for Linux, yet alone the entire development environment, and unless there is a compelling business reason to do so, I don't see this happening in the future.

I saw this question a while back but wanted to verify/check before responding so I can verify that using the latest wine 1.4.1 you can run the Uniface IDF under the latest Ubuntu 12. In fact the folks at winehq have improved it as my previous tests on Ubuntu 10 did require some standard windows dlls. So far as I can see this latest release does not need them although I have not tested to a great depth, but it does work. Yes I know aside from dlm it's not native but then again neither is .net under the mono equivalent. The setup is identical to my previous postings.