They spread via runners but spread is slow and you may find it disapointing as a ground cover unless you plan on planting many and spacing close. Grow in partial shade...the deeper the shade the slower to spread.

Vera

Forgot to mention that the standard Mondos have a fast growth rate and can quicky become invasive. My first post was regarding the dwarf varieties.
Vera

I started with 3 clumps, and after a while I divided them into more clumps, but they don't spread very fast. Dividing them frequently would probably spread them better than waiting for them to fill in by themselves.

I had great success taking the black berries off a friend's plants. I put them with pool filter sand between two boards and ground them up. I planted them in trays, sand and all. Next Spring I had many started up.

I thought that many berries are eaten by birds and pass first into a gizzard. This is a tough sack that the birds actually fill with sand. It helps grind up food, since birds have no teeth. I tried to imitate this by putting the sand and berries on a board and laying another small board over it and rubbing the two together. I just distributed the mess among several planting trays on top of the soil and watered them. I put them somewhere safe from sun, soaking, drying or wildlife.
I tried this with Ilex verticulata berries also, without success. I may try again.

Since we're talking about mondo grass in this post, I have dwarf mondo grass at the edges of my garden. I'd like to spread them (move them around) so that the clumps will look a bit more even (some clumps have spreaded much more healthily than others).

I didn't realise they have berries, but is it ok to just pull out the far clumps and replant them where I want them, and water? I think they might be hardy and not die that easily from the shock. Is this ok?

Many thanks in advance :)

Yes, you can transplant the clumps, but please use a trowel to dig them.