If in fact you are making Widgets, you will need to use the legacy Plugin Framework, which works for on-Premise and Hosted instances of Jive, but doesn't work for Cloud.
If you'd like to work for Cloud, I would recommend pursing a possible Add-On solution.
most specifically an App sounds like what you might be interested in:
Depending on which path you take (and your infrastructure), you will have varying degrees of "develop/test" locally success, but we have a lot of tooling that can help with giving you an agile development experience.
Hope some of this helps steer you in the right direction.