Is it possible to use COLLADA with C?
The current implementation of COLLADA DOM is written in C++, so I’m wondering if there is some C wrappers around…

Well since Collada is a schema-based (rather than API-based) format it’s perfectly valid to read and write Collada documents using any language you want. However the Collada DOM is C++ only and I’d be surprised if there are any plans to change that. If you have to use C you could either read/write the xml yourself or use an xml parsing library like libxml.