There is another one alternative, rump kernel[1], mentioned in commentary to original posting about "direct" network processing[2]. The recent development was discussed in LuaJIT mailinglist recently (the thread is interesting by all means in "minus OS" context by the way)[3]

[1] http://www.netbsd.org/docs/rump/

[2] http://erratasec.blogspot.ru/2013/02/custom-stack-it-goes-to...

[3] http://thread.gmane.org/gmane.comp.lang.lua.luajit/2493