There is a discussion (http://www.cruisersforum.com/forums/f134/charts-31346.html) on the opencpn forum about the topic.

The issue is not only the file format. Actually that's the easy part. The trick is to geo-reference them properly.
Ozi explorer has a tool for geo-referencing tiff files, but Ozi is somewhat slow as a navigation tool. Opencpn is better, but it doesn't have a tool for geo-referencing.

Short answer: with libbsb and some other software (http://www.cruisersforum.com/forums/f134/mc2bsbh-mapcal-template-to-bsb-template-conversion-32337.html) you can create usable geo-referenced raster charts.

Incidentally, Opencpn is great for actual navigation. One of the few shortcomings is that it only handles mercator projections. The software does not use the "proj4" package, instead they developed their own (faster?) tools, which I lament. Runs on gnu/linux, macs and windope.