Migen is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 3 of the License. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. Additional permissions under section 7 of the GNU General Public License (GPL) are hereby granted. The purpose of this exception is to allow non-GPL (including proprietary) logic cores to be used in conjunction with code generated by Migen in a design. "Generated" code refers to Verilog or VHDL code that has been obtained by converting FHDL structures using Migen. To "instantiate" is to include and connect another module as specified in section 12.1.2 of the IEEE standard 1364-2001 or in section 9.6 of the IEEE standard 1076-1993. (1) You have permission to propagate a work of generated code that instantiates modules that are not generated code and do not comply with the GPL. (2) You have permission to propagate a work of Verilog or VHDL code that is not generated code, does not comply with the GPL and instantiates generated code. The availability of this exception does not imply any general presumption that third-party software is unaffected by the copyleft requirements of the license of Migen. Unless otherwise noted, Migen's source code is copyright (C) 2011-2012 Sebastien Bourdeauducq. The simulation extension (as mentioned in the comments at the beginning of the corresponding source files) is copyright (C) 2012 Vermeer Manufacturing Co. Other authors retain ownership of their contributions. If a submission can reasonably be considered independently copyrightable, it's yours and I encourage you to claim it with appropriate copyright notices. This submission then falls under the "otherwise noted" category. All submissions must use a license compatible with the GPL and the exception above.