CGM Open BHO Project – CGMOPENBHO.DLL
Cgmopenbho.dll installs with the CGM Open BHO Project. This Browser Helper Object (BHO) allows software vendors to build WebCGM viewers that can handle object-level WebCGM addressing when running inside Microsoft Internet Explorer. WebCGM has to do with using vector/raster graphics in web pages. You'll find more information at http://www.cgmopen.org/technical/bho/index.html. If you're not a developer, it's likely that you can get by without this file.
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CGMopen.org