OpenMetrics relates to the metrics part of OpenTelemetry, where the latter is currently in alpha/experimental phase. OpenTelemetry has a statement on being interoperable with OpenMetrics for both accepting, forwarding and generating in the OpenMetrics format [0]. So they are two separate CNCF projects where OpenMetrics has overlap with a part of OpenTelemetry.

[0] https://github.com/open-telemetry/opentelemetry-specificatio...