Is there any way to have more than one character?

Unfortunately the answer is No. Your character is kept on a central remote server that is tied to the CD key of your game. So with out buying a separate game and installing both keys it is not possible to get two characters.

The other option that you will run into from time to time is when a server is not hooked up to the central repository in which case your character exists on that server and that server alone. This is generally against the server agreement with the developer of DayZ however so these are very rare and often mistakes in configuration.

There is actually a very easy way to get a second character. But you have to buy an additional copy of ArmA2. I didn't necessarily mean to find this out but a friend bought a copy of ArmA2 for day z, he didn't like it. So before he uninstalled it, I went into the registry and got a copy of the ArmA2 CD key and exported it. Then I went into my own registry and exported my ArmA2 CD key. Both were saved as a .reg file. I then emailed that file to myself and put it on my computer. Now when I want to play using his character, I run the .reg file to install his CD key in my registry before starting ArmA2.