These geese are far beyond the age of normal imprinting; they have essentially adult plumage, so they are several months old, if not older. Imprinting tends to happen in the first hours or day after hatching. It's possible that these geese were raised by other humans and then released wherever the Rods found them. It's also possible that these have been fed by humans since hatching, and that the Rods gave them food and they followed them home. Either way, while it's cute, it's not a good idea, and it's illegal to keep them without a permit.