However, it's pretty disappointing that OpenAI, a non-profit organization that claims to want to distribute AI as evenly as possible, to not release the source code of their research to make their findings reproducible by others. This paper is an example, but also other high profile work, such as their DoTA bot.
Edit: My mistake, this paper was open sourced, see below comment.
The code is linked from the top of the blog post: https://github.com/openai/random-network-distillation.
While we do produce lots of open-source code, our mandate is much broader than that: https://blog.openai.com/openai-charter/. We are attempting to build safe AGI and distribute its benefits.
In the short term, that means we focus on building working systems and will sometimes, but not always, release source code.
In the long term, per the charter: "we expect that safety and security concerns will reduce our traditional publishing in the future, while increasing the importance of sharing safety, policy, and standards research."