They did it. It's done. General Dynamics C4 Systems and NICTA released seL4 under an open source license. I've been wishing for this since 2012, when I bookmarked the seL4 papers under security research.
Oh for time to study all the details! The formal model of C, the translator from C to Isabelle, and on and on.
I wonder what it would take to put node-js on seL4, with no linux kernel in between. Then, using secure-ecmascript and such, we might have a complete capability based platform.
Meanwhile, sandstorm is an emerging personal clound platform with a capability security architecture (cap'n proto etc.). I pitched in to the kickstarter campaign because I really want to use it but I doubt I'll find time to host it myself.
But what really surprised me was that while wrestling with some python/R foreign function interface issues, I discovered this bit of rserve news:
Additions in version 1.7
... Another major change is the new, optional object capability mode in which all commands are disabled except for CMD_OCcall. In this mode the server does not send an ID string, but instead sends a regular QAP1 message with CMD_OCinit. This message is guaranteed to have at least 16 bytes of payload so it will satisfy the read for an ID string. The command has been chosen to correspond to "RsOC" (in little-endian) as to identify this mode. The payload is DT_SEXP which holds all initial capabilities that can be used in CMD_OCcall. Each CMD_OCcall is DT_SEXP encoding a call (i.e., LANGSXP) with an OCref object in place of the closure. Rserve will de-reference it before calling eval. The main purpose of this mode is to create a basis for a secure interface where arbitrary evaluation is not possible. Only code exposed by capabilities can be executed.