Working on it...
The LatticeMico32 toolchain (gcc, gdb, ar, ld) is very bad, seriously... I'm thinking of doing a MIPS or ARM emulator, just because the toolchains are so much better to work with.
Anyways, I do have a framebuffer demo that runs at a very decent frame rate on my machine (at this moment it is Chrome only and I unfortunately don't have the binaries for the demo on github). But this is not on Linux, it's on a barebones newlib environment (no Operating System).
Writing a mouse interface is trivial, the only reason I haven't done it yet is I'm thinking if it is worth to continue investing on the LatticeMico32 architecture, as the toolchain makes me want to pull my hair out.
Besides running Linux, the emulated system also runs RTEMS (actually it runs anything as long as you can get the toolchain to produce working binaries), and it might be easier to get an RTEMS system running with a simple graphical environment, but then there wouldn't be man y libraries do choose from.
So that's the status. I believe we are on the verge of having a viable option for making "GUI" programs on a canvas screen. If I were to work full time on it, I could pull a prototype off in about a month or two (literally), maybe a little less as this thing is so addictive I would easily work 16h days on it if I could.
IMHO, the ideal thing would be having an easy to use environment with a mature toolkit on it (I was thinking Qt) and let the user choose the language of choice to develop in. Possible choices would be C, Python, Ruby and Lua, which are fairly easy to have on the web.
Technically, it can be done, I just don't know if there would be enough interest, and how to have a sustainable business model around this idea. What do you think?