>We knew up front that, whatever solution we picked, it should be accessible, easy-to-use, free and preferably open-source.

I'm not a Microsoft Word fan, but why does their tool need to be free and open-source?

They went to great lengths to explain how the performance of the tools is so important; only to exclude anything you might have to pay for or is closed source.

Who cares if you have to shell out a few bucks for something if it works well and provides great value (i.e. saves you more time and hassle than the money you paid for it)?