A running droplet cannot be migrated but you can transfer a snapshot of your droplet. To do this:

1. Power off your current droplet.
2. From the control panel create a new snapshot of the droplet.
3. In the images section of the control panel, find your new snapshot image. There is an option to transfer the image to another account. Enter the email address of the other account to begin the transfer.
4. Once you accept the transfer on your new account you can use the snapshot (rather than a default OS image) to create a new droplet which will be a clone of the existing one.