Here are a couple more resources where the lead gives a bit more description:

http://on-demand.gputechconf.com/gtc/2015/presentation/S5276...

http://www.slideshare.net/kaigai/gpgpu-accelerates-postgresq...

edit: His slideshare page http://www.slideshare.net/kaigai has even more recent presentations. I've only had time to skim much of slides, but it seems he's flip-flopped a couple of times between OpenCL and CUDA