"Any one that won't let Bedrock's tools and clients complain" is the answer - I know nothing about what the author's hinting wrt his future plans, but my impression's that the current release's a fairly light layer of mostly shell-scripted userland tools with only one needing compilation ("bedrock chroot"); Kernighan would be proud. (Those who treat the Unix Haters' Handbook as a source of design maxims would simply conclude a runtime built upon an introspectable and introcessionable language would obviate the need to marvel at the engineering involved here. The initial effort involved here, to be fair, is orders of magnitude less.)