According to the activity log @Rolf Kalbermatter is the only active user for at least the past 6 years (log ends there): https://sourceforge.net/p/opengtoolkit/activity/?page=1&limit=100
@jgcode compiled a nice list some time ago. Not sure if all of these are done yet:
Here are some ideas that come to mind:
Allow the community to participate in the project (create and maintain tasks/issues/features, add maintainers, add admins, etc...)
Bring back openg.org (could be a different domain) and allow the community to contribute to the site via pull requests
Split the monolithic repository into separate repositories for each project for best practice (and to prevent linking between projects)
Convert the SVN repository to Git to allow offline branching, pull requests, etc...
Use tags when releasing new versions, this allows everyone to use a prior version if needed.
Add documentation for how to deploy new versions (the building process).
Add documentation about which LV versions to use and what tests to perform before opening a pull request.
Use a single license for all projects.
Add a CLA to ensure the license holds for all contributions
Work on Feature requests, bugs and change request (there are a lot)
Share your thoughts
SF is a good place for a small team of developers, working on their project. Users are only meant to report issues and make feature requests. All development is taken care of by the admins/maintainers. Although there are ways to do pull requests, they are very inconvenient and tend to scare potential contributors away.
In my own experience, there are a few ways to revive a project like this:
Get the original admins back to the project (unlikely, they left for their own reasons)
Add new admins/maintainers who have full authority over the project => Requires at least one responsive admin / SF is difficult for contributors (compared to GitHub)
Do what @Michael Aivaliotis did. Archive the original code base, move to a simpler platform and build on top of what is currently available.
Option 3 is most likely to bear fruit.