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README.md
+Build a Secure EcmaScript (SES) environment atop an ES6-compliant platform,
+enabling safe interaction of mutually-suspicious code, using
+object-capabilities.
+
+Derived from the Caja project, https://github.com/google/caja/wiki/SES .
+
+Still under development: do not use for production systems yet, there are
+known security holes that need to be closed.
+
+Incorporates (as a git submodule) the Realms shim from
+https://github.com/tc39/proposal-realms .

add basic README