Brake fluid to the touch is very strange feeling, and will destroy paint, not like oil. Considering it's brown in color! can mean its fluid from the rear end, brake lines and related parts, shock fluid, or even the top fluid, to check if its top fluid you need to run the top up and down a few times and then check for leaks, Saab's that have convertible tops have had the same problem, and it takes a little time for the fluid to leak out through the bottom of the car, make sure you check the cylinders for seapage as well.