Yoric - the Binary AST size comparisons in the blog - was the original javascript already minified?

On our sample, x0.95 for minified code (so that's a 5% improvement) and ~x0.3 for non-minified code.

As usual, read these numbers with a pinch of salt, they are bound to change many times before we are done.

Does BinJS perform AST transforms like `!0` to `true` which would be shorter in binary AST encoding? Or does it faithfully model the original code?

It faithfully models the original code. The idea is that if you want to transform `!0` to `true`, or if you want to obfuscate, etc. you can always plug an additional tool.

The 5% gains over minified code are impressive given that BinJS performs no AST manipulation.

The BinJS prototype will be written in pure javascript I assume to speed its adoption?

For the moment, it's JS + Rust, because Rust is better than JS when you keep refactoring Big Hairy Data Structures. However, once the data structures stabilize we're planning to shift it entirely to JS.