The first proof of concept of Oozaru is up (running the Spectacles battle engine), check it out:

• https://fatcerberus.github.io

Consider this Alpha 1.  I won't call it a beta, since it's not quite feature-complete yet; sizeable portions of the Sphere v2 API are completely missing and/or inoperable.  Like, the Joystick class exists, but all methods are no-ops.  And almost the entire FS API is missing... that kind of thing.

Hey! I haven't been around for a while but this is looking mighty impressive so far, good job!

Here's the above demo, now available directly on the SphereDev website:
https://oozaru.spheredev.org/

I have been playing a game called CrossCode lately and it's clearly HTML5 based engine, but they had console releases, which gives me hope on Oozaru... I might think about using Sphere again. I was toying around with Game Maker, but I think it may be easier to build the game in Sphere? How's the performance?

It uses WebGL, performance seems pretty close to desktop Sphere as far as I can tell.  I had a perf issue a while back where it was really slow on Apple platforms, it turned out it just didn't like me reusing VBOs for Shape.drawImmediate(), even when they were created with the dynamic flag.  It ended up being way faster just to throw away the vertex buffer and create a new one next time.  But otherwise, there are no performance issues that I can see, and even that issue has since been fixed.

There are a few undocumented hoops you have to jump through in order to ensure your code runs as-is in both miniSphere and Oozaru, mainly having to do with module import conventions (they won't be undocumented for much longer, and I'm planning to add a compatibility mode to enforce them), but as long as you don't touch the Sphere v1 API, as long as your game runs on the desktop it should run fine on the Web too. That was, after all, my main goal for Oozaru. 

The first official beta release of Oozaru is finally out: version 0.4.0!
https://github.com/spheredev/oozaru/releases/tag/v0.4.0

To make it as easy as possible to dive in, Sphere Studio 2.2.0 was also just released and supports testing games in Oozaru locally.  Just unzip the Oozaru distribution to a folder of your choice and point the IDE at it and you're good to go!
https://github.com/spheredev/sphere-studio/releases/tag/v2.2.0

Just released 0.4.2 which removes the requirement to use Chrome.  The engine will now run in Firefox and Safari as well.