dcos-metrics is maintained by Mesosphere, but as a proudly 100% open-source component, we welcome and encourage community contributions. Contributing is as simple as opening a PR.
If you'd like to add functionality or fix a bug, it helps us get your PR merged quickly if there is a corresponding ticket in JIRA, but it's not essential, especially for small changesets.
If you'd like to talk about your project before you start coding, the maintainers hang out on DC/OS Community Slack in the #day2ops channel. If you make regular contributions (or you'd like to) please consider attending the Day 2 Ops working group, where we discuss the direction of dcos-metrics and related components every month. There's a dedicated slack channel for that too - #day2ops-wg.
We look forward to seeing your contributions.