So you've developed a killer plugin and you want to share it with the world. How do you do it? This page gives you an outline. For complete information on making your plugin available on the Atlassian Marketplace, see Marketplace documentation.
Once you're happy with your plugin and ready to release it, use the SDK to package your plugin.
This will produce a file in the plugin's directory. You can use the UPM to install it for testing in your staging or production environments.
If you're going to be distributing your plugin, it's a good idea to explicitly license your software. There are many choices, and for the most part you are free to choose whichever one you'd like. The only caveat is that you can't use the GPL, as Confluence and JIRA are not themselves GPL'd. (There is much argument about this point, but we've had GPL authors complain, and we'd rather err on the side of doing the right thing.)
If you don't know which license to use, we generally recommend the Apache2 license. It simple and completely open: people are free to do whatever they want to the software, and you're free of any liability. It's the license we use for most of our plugins.
Of course, you're also free to charge for your plugin, if you want. If so, you should create an appropriate commercial software license. You can also sell your plugin in the Atlassian Marketplace, available from plugins.atlassian.com. See here for details.
One of the best reasons to share your plugin is that you might attract other developers to help you with it. In order for them to do that, you'll need a way to share source code. Atlassian offers free Git and Mercurial hosting on bitbucket.org.
Of course, you're also free to host it on any service of your choosing.
As soon as you make your plugin available, the very first question people will ask is, "where can I file feature requests and bug reports?" Handling such reports through email will become unwieldy almost immediately. Make sure an issue tracker, such as JIRA Cloud or Bitbucket, is available. In all cases, take care that your plugin's entry on the Atlassian Marketplace takes users to it.
Your packaged plugin must be accessible on the Internet in order for users to download and install it. The easiest way to do this is to list your plugin on the Atlassian Marketplace. Alternatively, any other file hosting service (such as a public Dropbox folder) is suitable.
Provide detailed information about the plugin's abilities, limitations, and requirements. Use Confluence Cloud, BitBucket's wiki, or your own site. Make sure it's linked from your plugin's Atlassian Marketplace entry.
You should also announce the release of your plugin on Atlassian Answers, where you can reach hundreds of potential users or customers.
Once people start to use your plugin, they're going to want to get involved. Some people will file bugs. Some people will request new features. And best of all, some users might pitch in an add new a feature themselves. You can encourage this behavior by being responsive, answering questions, making fixes and additions as quickly as you can. Demonstrating momentum is the surest way to keep people interested and motivate them to contribute themselves.
Each time you release a new version of a plugin, there are certain steps you should perform.