Here is another version of this plugin
it has its own bookshelf and can be used from the SD card, without that modified firmware. One has to unpack the archive to the SD card and go to directory "/java" and open book SGFViewer.exe.fb2, then select the folder with .sgf files and open one of them.
It works on Hanlin firmware (EN2.00) and all versions of that modified firmware. It also works on bebook's firmware but if you can see those annoying moving "arrows" when you open fb2 files, then those arrows will annoy you also in that SGFViewer (probably it will be solved in the future).