LightWorks is a software product currently owned by EditShare that has won scientific and technical Academy Awards and Emmy Awards, has been used to produce a number of popular films, and has many other "wins", is being open-sourced. Work on the LightsWorks software was started over two decades ago, but only recently was it acquired by EditShare, and they now find it in their interest to open-source this code. Shutter Island, Centurion, and Hitchhiker's Guide to the Galaxy are among the films that have been edited using Lightworks.
Lightworks Open Source as its known is expected to be released in the third quarter of this year as a free download. It's a pity that the code cannot be immediately accessed, but you can sign up to stay informed on the process. Hopefully this means the soon-to-be-open-sourced code is currently undergoing some revitalization and being brought into a state where it's more likely to succeed as a free software project with documentation, a clean build process, etc.
As was said in their press release announcing this open-source endeavor, "EditShare is completely committed to turning out a superior professional editor through the Lightworks Open Source program. We are increasing our development and support staff, and all contributed code will be thoroughly managed by our distinguished Lightworks team, ensuring the reliability of the new Lightworks Open Source editor."