OpenFire
The OpenFire Processor Core is an libre-licensed soft-microprocessor originally written by Stephen Craven and improved upon by Alex Marschner PhD and masters students, respectively, of the Configurable Computing Lab. It is written in Verilog and is binary-compatible with Xilinx's proprietary MicroBlaze soft-processor. The OpenFire was created to facilitate research on single chip, multiple processor configurations and application-specific instruction sets. The OpenFire core is released under the MIT license.
The OpenFire core can operate at 50MHz and has 8 output ports and 8 input ports. It features on-chip peripheral bus support and directly uses BRAM, eliminating the latency of the local memory bus. Version 0.6a was released on December 12th, 2007.