I've had some interest from people about open sourcing LastCalc so that people could help me work on it. I liked this idea but I was concerned about someone simply cloning the site and not contributing their improvements back to the open source project (which, as a web service, the GPL wouldn't obligate them to do).
It's the GNU Affero General Public License which is designed to address exactly this issue.
So, if I were to open source the code under this license, and put a bit of work into explaining the codebase to people, would anyone be interested in contributing? It's implemented in Java, with heavy use of JQuery in the front-end, all built on Google App Engine.
I think the key stuff that LastCalc current lacks are the ability to have user accounts, and the ability to publish worksheets, and also import them - so that people can share their creations and we can build up an ecosystem of useful tools.
Thoughts?