One thing to consider, if your studios is at home, is looking into your home insurance policy and if it covers public liability while folk are visiting your studios. You can find this out by looking at your policy and/or contacting your insurance provider.
Basically Public Liability Insurance is a requirement of this program because the councils supporting the project want to be sure that they will not be liable if anyone is injured at the event. So any policy that will cover visitors to your home/studio will do the trick and you may already have a policy that does just that.
If not the second option is a policy for artists provided under an umbrella scheme. There are a few organisations that offer this at reasonable rates they are:
Regional Arts Victoria
Arts Workers Alliance
Artsource (check out Max membership)
If you ever intend on running workshops (in your studio or elsewhere) having such insurance is a really good idea anyway.
I hope all this helps. And please feel free to contact me if you need any further information.
Open Studios Project Coordinator
Ph: 0410 583 972