There are a lot of games on the DS whose origins are in free online games. Some, like Diner Dash, Nervous Brickdown, and the upcoming N+ and WordJong, are good, or even great. Some are Elf Bowling 1&2. In every case of a free game getting remade as a DS cartridge, money is charged.
Do you have any games based on freeware? Do you plan on getting any in the near future? Is compelling gameplay enough to warrant a purchase for a portable console, when the experience can be had for nothing on PC? Or do you require significant expansion and upgrading before you'd even consider it?
Our personal view: even if a game costs nothing, that doesn't mean it has no value. We don't want to pay strictly for portability, but we're entirely willing to shell out for new content in a game whose progenitors were once free. Not Elf Bowling 1&2, though.