Yeah. I used TI-RTOS a couple of years ago for some work and the whole experience was very different. The most unique part was that the RTOS came bundled with a development GUI integrated into the IDE where you could create threads, mailboxes and other such RTOS primitives. I don't think I liked using it very much though.

Surprised to see that they killed the project.

What was the licence? Did you have to run it on TI parts or something?

BSD license according to this: http://www.ti.com/tool/TI-RTOS-MCU#descriptionArea

It does compile with gcc, but I don't trust it with gcc. At least with TIVA TM4C processors, it would not boot. I suspect they don't test with gcc as well as with their own compiler.