Stallman stated that "the plans aimed for low cost, enabling many children to use the machines, and free software, so they would have freedom while using them." From what I understood, the goal of the project was to get computers into the hands of children in third-world countries, so they could simply get experience with computers -- period. It was my belief that the fact that free software was used was simply out of convenience; since free software was also free (as in beer), it was another step in cutting the costs of the laptop.
When Microsoft stepped in and "offered up" its OS at the extremely cut costs, Negroponte decided that would be a more useful option; I don't think his intention is to force-feed proprietary software to children. Either he believes Windows is a better option, or he is an economically self-serving individual. Regardless, I sense that the ultimate purpose of this project was unclear to certain people.
On a less direct note, I can't stand Stallman's zealotry. It's great that he is able to stand so firm on one particular point, but it is also a terrible trait, considering that he isn't willing to even give a moments consideration to alternative options on a scope/level _outside_ his "cause."