Yes, the B+ has a 40 pin connector instead of the 26 pin header for B and A. The good news is the pinouts of the first 26 pins of the B+ 40 pin connector are the same as B and A. So if the OpenSprinkler board will physically plug onto the B+, it will make the correct electrical connections.
Just eye balling the B+ it looks like it might connect OK with the OpenSprinkler board, but the only way to be sure is for someone to try it, maybe Ray will.
I think it’s unlikely the B+ will fit into the OpenSprinkler enclosure, and for sure some of the connectors won’t line up with holes.