What do you think is important for explaining Glest/megaglest to persons that are not familary with OpenSource Games.
I would explain that Free Software games are developed under very different conditions than proprietary games and explain the differences, so that readers will know that it is not fair to just compare the features a proprietary game provides with those of a Free Software game, but you also need to take the funding, development team size, administration team size, advertising / marketing budgets and many more things into account. Using Free Software is a bit like choosing to buy fair trade food: by accepting some detriments on your end (possibly higher price for fair trade goods, possibly lower quality for Free Software), you add to a greater good (less slave-like working conditions for fair trade goods, spread of Free Software and its very positive side effects on the software side). I'm not entirely happy with this comparison, though, since fair trade is often really about peoples' lifes (and deaths), Free Software liberates things on a very different level which usually doesn't impact on whether or not people die young or must live an unbearable life. Still, I find there are some similarities in the concepts of fair trade and Free Software.
This iwas an idealistic approach for an explanation. For people who are less idealistic, it might be good to point out that Free Software games are usually available free as in beer, too. And that this can counter balance the quality differences there can be between proprietary and Free Software games. Obviously, the argument of "but I got this pirated game for free, too" is void.