I've contemplated going through OpenAI's guide Spinning Up in Deep RL. It's one of many resources OpenAI made available, and builds upon the OpenAI Gym system of environments for training deep reinforcement learning agents. They range from very simple text-based environments, to 2D Atari games, to full 3D environments built with MuJoCo. Whose documentation explained that name is a shorthand for the type of interactions it simulates: "Multi Joint Dynamics with Contact"

I've seen MuJoCo mentioned in various research contexts, and I've inferred it is a better physics simulation than something that we would find in, say, a game engine like Unity. No simulation engine is perfect, they each make different tradeoffs, and it sounds like AI researchers (or at least those at OpenAI) believe MuJoCo to be the best one to use for training deep reinforcement learning agents with the best chance of being applicable to the real world.

The problem is that, when I looked at OpenAI Gym the first time, MuJoCo was expensive. This time around, I visited the MuJoCo page hoping that they've launched a more affordable tier of licensing, and there I got the news: sometime in the past two years (I didn't see a date stamp) DeepMind has acquired MuJoCo and intend to release it as free open source software.

DeepMind was itself acquired by Google and, when the collection of companies were reorganized, it became one of several companies under the parent company Alphabet. At a practical level, it meant DeepMind had indirect access to Google money for buying things like MuJoCo. There's lots of flowery wordsmithing about how opening MuJoCo will advance research, what I care about is the fact that everyone (including myself) can now use MuJoCo without worrying about the licensing fees it previously required. This is a great thing.

At the moment MuJoCo is only available as compiled binaries, which is fine enough by me. Eventually it is promised to be fully open-sourced at a GitHub repository set up for the purpose. The README of the repository made one thing very clear:

This is not an officially supported Google product.

I interpret this to mean I'll be on my own to figure things out without Google technical support. Is that a bad thing? I won't know until I dive in and find out.