Is Steamworks for Unity Indie free?

I want to start doing all the extra steam features to my game and I don't want to buy Ludosity's wrapper, so I'm going to use the Steamworks SDK.

I've read up and some people say that if you use Steamworks with Unity Indie (Free version), some things won't work (something about 'Native files') so I'm not sure what to do at this stage.

Any reassurance/advise would be very helpful.