This can be done, and in fact there is a business in it too: an open source competitor to Lexis and Westlaw. Data entry is bound to be a problem, as no-one is going to want to give up electronic data, but I for one would be willing to spend a few hours a week transcribing documents at the local courthouse.
>>javajo+(OP)
You might enjoy the free legal data service offered in Canada that has most of the cases that you can find on Westlaw/Lexis: canlii.org. It could be more open, but it's free and works well.