Read about "Soft Device" - it is delivered as a hex file loaded into the IC separate from your Application code. The "Software Development Kit" includes the header files and examples to access the BLE in the soft device.
Today could try starting with SDK6.1.0 (first install SDK6.0.0 if you want BLE UART experimental code), and also s110v7.1.0 (soft device), but to access many things you will need a Product Key delivered with the EK, DK, or some of the third party kits.
See the Blog for "Getting Started".
Low cost may be to start with nRF51822EK or one of the third party options, may prove useful to have the full nRF51822DK + nRFgo Starter Kit.
The SDK has full support for GCC (Makefiles, linker files). You can add a custom service using Keil, IAR, or GCC. The SoftDevice comes as a binary file, so there's no need to compile the stack along with your application. Just use the appropriate header files in your application and load the SoftDevice in flash using the nRFgo Studio tool. There's a "getting started" guide in the Evaluation Kit User Guide. Follow the instructions to register a MyPage account (included in your Eval Kit) and you get access to all downloads; SDK, documentation, User Guide, softdevice, tools
The SDK has full support for GCC (Makefiles, linker files). You can add a custom service using Keil, IAR, or GCC. The SoftDevice comes as a binary file, so there's no need to compile the stack along with your application. Just use the appropriate header files in your application and load the SoftDevice in flash using the nRFgo Studio tool. There's a "getting started" guide in the Evaluation Kit User Guide. Follow the instructions to register a MyPage account (included in your Eval Kit) and you get access to all downloads; SDK, documentation, User Guide, softdevice, tools
