It depends on what Contax mount you are talking about. The G2 lenses cannot be manually focused without being on the body, so those have to be converted.
I have seen an adapter for the Contarex mount (not ContaFLEX) - so there is the potential to use Contarex lenses on the GH1 - Contaflexes could be possible eventually with the right adapter.
The C/Y mount began in the early 70s (maybe some late 60s? Not sure on that) - and that's where you find the classic, legendary Zeiss 35mm SLR lenses: 18mm f/4, 21mm f/2.8, 28mm f/2, 35mm f/1.4, 50mm f/1.4 (and rare f/1.2), 85mm f/1.4 (and very rare f/1.2), etc. etc. etc.
As far as I can tell, the mount I have is just called the contax mount. It's from their early rangefinder cameras (Contax II) and the lens is a collapsible Sonnar 5cm f2.