Even if it don't seem like a long term project, I'm almost sure there's a pretty good chance at the guy releasing the sourcecode. Seeing how the sourcecode for the original danmaku on the site is available.
These are the links found in the video:
Featured before the developer's site, stating that the game uses the psp bitmap font library created available at the site:
http://www.psp-programming.com/benhur/And this is the other link featured in the video at the loading screen after the previous link:
http://dixq.net/rp/It goes to what seems to be the main page for their original shooter, and the main site is of course:
http://dixq.net/Where you can also find the zip file index at:
http://dixq.net/zip/And in the zip index I also found the youmu.zip file I mentioned earlier. However the youmu zip seems to be corrupted, but the files listed in the zip is all those of PCB.
Hopefully there's more info about the touhou port, somewhere on that site. But yea, since my Japanese reading skills are pretty low at the moment, I can't really know for sure.