i dont know of wii homebrew but in the nds space there is BlocksDS which is not part of devkitpro, and in gba space you can get (experimental) toolchains from wf-pacman (wonderful toolchain). sadly, the nintendo homebrew space is ruled by devkitpro, and i spent some time trying to find an alternative to it, but that doesnt seem to exist right now.

just realized you asked for something different, and my comment above is on the wrong subject. either way, i dont know of any big library/toolchain/sdk for the wii not from dkP, so the chances of a loader different from hbc and not based on libogc are small, sadly.