There is a gcc compiler environment for MSP430, and you can run it on linux and Macs. There is a somewhat active community (not as big as you'd expect based on the number of launchpads "sold", but pretty significant.) The msp430 gcc compiler is under active development (active enough to be "exciting", in both good and bad ways. One of the relatively recent developments (since launchpad was first released) was an arrangement with TI whereby the gcc environment can (and does) use TI-provided include files for the chip-specific peripheral definitions. This isn't as good as if TI supported the gcc environment themselves, but it's a lot better than having the gcc community have to maintain all those files themselves! (a lot of the other recent development has to do with supporting the "extended address" (>64kB) MSP430s...)