Downloading C4DtoA for Cinema4D R17 1.3.0 from the developer's website was possible when we last checked. We cannot confirm if there is a free download of this software available. This program is an intellectual property of Solid Angle. The most popular versions among C4DtoA for Cinema4D R17 users are 1.3 and 1.0. The program relates to Photo & Graphics Tools. We recommend checking the downloaded files with any free antivirus.
From the developer:
Arnold for Cinema 4D (or C4DtoA) provides a bridge to the Arnold renderer from within the standard Cinema 4D interface.
You may want to check out more software, such as ShiVa Editor, which might be similar to C4DtoA for Cinema4D R17.