The work and challenges for OpenWorm may not reflect the work and challenges for the Human Brain Project. Among other things, unlike most other neurons, C. elegans neurons don't spike. Action potentials make simulation more tractable since you only have to worry about propagating spikes, and not all internal state, between connected neurons. (At least ignoring things like ephaptic coupling, which is probably not that important in mammalian neocortex.) Also worth noting that the Blue Brain project supposedly succeeded in simulating 100 neocortical columns, which is 1 million neurons, vs. 302 neurons in C. elegans.