Pascal, from which perspective would you like to get the bundle version?
From the Bundle itself:
org.osgi.framework.Version version = org.osgi.framework.Bundle.getVersion();
Through the resolver API (arguably a little trickier):
Map<org.osgi.resource.Resource,List<org.osgi.resource.Wire>> results = org.osgi.service.resolver.Resolver.resolve(org.osgi.service.resolver.ResolveContext ctx);
Resource resource = results.keySet().iterator().next();
List<Capability> capabilities = resource.getCapabilities(IdentityNamespace.IDENTITY_NAMESPACE);
Map<String,Object> attributes = capabilities.get(0).getAttributes();
org.osgi.framework.Version version = (org.osgi.framework.Version)attributes.get(IdentityNamespace.CAPABILITY_VERSION_ATTRIBUTE);
There are a number of convenience APIs as well, but as I said earlier it really depends from which perspective you are trying... from a running framework or from some external agent analyzing a set of bundles.