SymPy Gamma: an open-source, Python-based alternative to Wolfram Alpha
I used to work at Wolfram Research on Wolfram Alpha's backend, and one of the most challenging technical problems we faced was free-form input. Although W|A has by no means perfected this, this is hardly an alternative - queries like "factor the number 100" fail because there is only the beginnings of a free-form transformer. Obviously, the usefulness of being able to answer "factor one hundred" is questionable, but W|A solved it out of Stephen Wolfram's aspiration to be able to "compute everything". Right now, this is just a programming language you can run on the web.The other thing is that W|A has trillions of data points and what I am only allowed to describe as the beginnings of a semantic network for inferring relations between them. It was a vastly overcomplicated system that was difficult to work with, so I am quite confident that some day there will be an open-source alternative that anyone can contribute to.The other thing to take into account is how this affects the future. Wolfram Research thought they were going to "disrupt the calculator" (I heard this ridiculous statement once at a meeting). In reality, Wolfram Alpha queries are more often for the sake of fun than for the sake of discovery (I know this because there was a big TV in the break room that would keep displaying things that people searched on Wolfram Alpha). Is it really that useful to be able to have a computer give you an answer to "I have two apples, Jill has three apples. How many apples do we both have?"http://www.wolframalpha.com/input/?i=I+have+two+apples%2C+Ji...Or is it more useful to make something that can take in symptoms of your current ailment and tell you which disease you are most likely to have? Wolfram Alpha does this as well.http://www.wolframalpha.com/input/?i=I+have+a+fever+and+a+ru...Although the results are difficult to interpret. In my time at Wolfram Research, I was certainly convinced by the idea of knowledge engines and their ultimate emergence, but I think the way this will be accomplished is in more in a Google-esque fashion where their knowledge engine results are displayed alongside a real search algorithm. Best of luck to the people on this project, I hope you make the first step into creating an open source knowledge engine.