freeware
Direct link to the Reference Gerber Viewer: https://gerber-viewer.ucamco.com
If you wish to run tests on Reference Gerber Viewer, sample CAD jobs are available for download here, under 'test files'.
If you wish to integrate this technology in your web application, this is possible, free of charge. Click here to download the html code to set up the integration.
Pulsonix, RS Group and Gemaddis are among the companies to have already done so. Read their testimonials.