TI BLE-Stack

Texas Instruments' Bluetooth low energy BLE-Stack software stack for TI’s CC2540 and CC2541 devices is a full-featured Bluetooth 4.0 stack that includes all necessary software to get started on the development of single-mode Bluetooth Smart applications.

BLE-Stack is available royalty-free to customers using TI’s C2540/41 Bluetooth low energy system-on-chip (SoC) family and also runs on TI’s first generation SensorTag, CC2541DK-SENSOR and remote control CC2541DK-RC development kits.
Two download links are provided here; version 1.4 that support CC2540/CC2541, and version 2.1 that support CC2640/CC2650.