It's useful anywhere information is structured and organized. Like file systems, mailboxes, chatrooms, databases, documents, presentations, product plans, code, libraries, laws, systems of laws, contracts, rules, server logs, guidelines, principles, docs, manifestos, journals, blogs, podcasts, server, clouds, etc.
If you're a programmer, beginning or advanced, no matter what kind of project you're working on, this imho should be part of your basic toolkit.
It's a bold move, I know. Maybe nothing will happen, but I don't think so. I think all kinds of greatness will come.
Right now there are a fair number of services that should have outliner interfaces, Evernote, Twitter and WordPress are at the top of my list. Now that I've become a GitHub user (no expert, by any means) I want to be able to organize my repo as an outline, and have an outline of all my repos.
I could use an outline editor for Google Groups. I am part of over a dozen of them. I really would like it to be just another outline in my browser-based desktop.
Now it's up to you to take it to all the places it can make a difference.
The GPL is the right license for our goals. We want to encourage developers to add features compatibly, so that all outlines open, and can be edited in all environments. If commercial developers want to add private features to the outliner, we will try to work with them. We just want to be sure we can have a conversation about compatibility, and perhaps create revenue to fund development. If a non-commercial project emerges that breaks compatibilty, because the GPL is used, we will have the option of bringing their work into compatibility.
And this is just the beginning. We need lots of docs, and hopefully a community will develop to work on that.
This is an exciting moment!
PS: I recorded a brief podcast about this release, as is customary.
PPS: Here's the FAQ announcing the open source release of Frontier in 2004.
PPPS: Here's an important 11-minute podcast about Concord and the GPL.