Believe it or not, this project (and this web site) is still alive!
I haven't started making use of the dual ARM core Hard Processor System (HPS) yet, so the MIDI software still just runs on the embedded Nios soft processor.
Since the DE1-SoC doesn't have an Arduino compatible connector, I had to replace the MIDI shield and breadboard built MIDI interface.
I build a slightly more permanent circuit on a Perma-Proto PCB from Adafruit with two MIDI inputs from the keyboard and the BCR2000 controller and one MIDI output for feedback to the controller.
On the short term horizon are the implementation in RTFM of two essential performance features: pitch bending and velocity sensitivity, but right now I am working on a simple MIDI sequencer to help me demo the synthesizer (there is a good chance that I'll be at the Bay Area Maker Faire again this year).