CDK4AVR stands for Cross Development Kit for Atmels AVR RISC processor serie
and should you support with a comprehensive Assembler and C development
environment for even this processor familie under Linux or similar host systems.
CDK4NIOS stands for Cross Development Kit for Altera's soft core processor NIOS and should you support with a comprehensive Assembler and C/C++ development environment under Linux. It will present only free of fee tools, so you can use it without risks.
CDK4MSP stands for Cross Development Kit for the Texas Instruments MSP430 MCUs and should you support with a comprehensive Assembler and C development environment for even this processor familie under Linux or similar host systems. It will present only f