The contrib area was a place to host adapters and application plugins submitted by the OpenTimelineIO community. Those contributions may have involved challenging external dependencies, and may not have the same level of support as the core.
The adapters previously found in the contrib area have been moved to individual repos within the OpenTimelineIO GitHub Organization.
New contributions should be created in standalone repos, and those can later be migrated to the OTIO GitHub organization after review.
The best way to get started is to go to the otio-plugin-template repo and click "Use this template". This will get you started with plugin boilerplate and allow you to develop the adapter in your own GitHub account.
Once you've developed your plugin, please contact the OpenTimelineIO team to talk about next steps for the plugin.