hardware: https://www.96boards.org/
boot: https://github.com/ARM-software/arm-trusted-firmware
toolchain: http://releases.linaro.org/14.11/components/toolchain/binaries/
In particular, the ARM trusted firmware project is what is supposed to save us from todays proprietary boot madnessI'm constantly amazed at how much work is done to reinvent the wheel as far as ISAs are concerned, SPARC is an excellent platform and has an extremely high level of "shovel ready" hardware designs that you can just ship to a manufacturer and get back hardware. There is even open VHDL to fabricate modern high power CPU designs.
Free/Open Source chips are a lovely idea that doesn't work without a financial sponsor because software can be made and distributed at near-zero marginal cost, including by the end user, but hardware can't.
So, why don't you do that? And if you wonder about others, especially big corporate guys, easy thinking would be that $100 isn't all you need to use SPARC, and it's cheaper for them to use something else. However, if you put it like that, you're a computer geek with zero insight into economics and marketing. The real answer is that it's more profitable for them to use something else than SPARC.
Microsoft have some kind of UEFI bootloader for the Pi2 for Windows 10 IOT.