Yeah I've seen their trees before some time ago and they aren't bad it's pretty cool they are giving them away for free, I'll have to look more into this. I'll have to be honest though, like the other guy said the sound was very sporadic so I found myself skipping around. I may have missed information on the details of the Free'ness of it.
They have a cinema 4d import plugin as well and you can also export as a fbx or obj from plantfactory for software packages they don't have a plugin for.