Pro_Stahl_3d - need verification on object enabler

I've received a file from a supplier, which contains a lot of proxy objects.

We only use Inventor and AutoCAD 2013 in our company - and we need to extract the files, and somehow convert them to Inventor. I've searched for solutions, and most people tell me, that I need an object enabler (probably for a Bentley product) - to do this task.

Can anyone confirm that Pro_Stahl_3D is created via a Bentley product - and what object enabler I need for AutoCAD 2013? (And maybe more importantly - is this object enabler free?).

Thank you in advance.