TI-RTOS

TI-RTOS: A Real-Time Operating System for TI Devices (ARM MCU Cores)

Its Free of Charge! Implements BSD Sockets and a full Ethernet stack.

Here is the PDF: http://www.ti.com/lit/ml/sprt646/sprt646.pdf

Official site: http://www.ti.com/lsds/ti/tools-software/rtos.page

SDK: http://software-dl.ti.com/dsps/dsps_public_sw/sdo_sb/targetcontent/mcusdk/1_00_01_74/index_FDS.html