This is a good move. I wonder why now, though? Possibly they didn't like to see things like the OpenTracing project adopting Datadog's APM libraries.
https://www.datadoghq.com/blog/opentelemetry-instrumentation...
https://www.datadoghq.com/blog/opentelemetry-instrumentation...
We're public so I probably shouldn't guess too much about the motivations beyond the explosion of interest in observability/kubernetes/cncf, but I do know there has been support for open sourcing these for a long time within the company and I'm glad to see it finally happen.
disclosure: I work at NR but my opinions are in fact cake and should not be used to make investment decisions (seriously that is a terrible idea I mostly invest in LEGOs and Magic cards)