How to share Drush code with the community?
If it's a useful Drush command, and one that you could see being used on a daily basis, the I'd suggest heading to the Drush issue queue and posting a feature request.  Then answer the feature request with a patch that adds the command.  Whether to not it's suitable for Drush core will most likely then be discussed and further action will be taken by the maintainers.

Another option as you mentioned, is to create a module form your command and submit it via the standard module submission process.

The last thing I would suggest it hassling the module maintainers on social media channels or e-mail. 

Greg Anderson does sometimes frequent this site though, so he might be able to provide a preferred approach :-)