The research is based on work I did writing and improving @DeepForger (http://twitter.com/deepforger), an online service for "basic" style transfer. The GitHub is a standalone version for learning and education, which doesn't do HD rendering as well yet and uses a bit more memory. The positive side, however, is that opening up the source code makes these ideas progress faster!
We'll try to integrate the idea of semantic style transfer into @DeepForger in the future, but this require quite a bit of work to get it to reliably understand portraits or landscapes without anyone's intervention. The fact it does require these semantic maps for all images makes it less straightforward to release as a service.
The semantic map remains static during the optimization, so it can be provided as a pre-computation (e.g. pixel labeling, semantic segmentation, etc.) or done by hand. The ones in the repository are done manually, but now experimenting with other algorithms. Anything that returns a bitfield or masks can be used!
Almost nobody in deep learning uses OpenCL. All the DL frameworks primarily focus on CUDA and that's where you get the best performance. OpenCL is off the beaten path and you pay for it in every way: support, performance, reliability.
AMD is going to support CUDA somehow too, I think that's a sign they admitted defeat on OpenCL for this.