Richard Stallman made it Yacc-compatible.
Wilfred Hansen of Carnegie Mellon University added multicharacter
-string literals and other features.
+string literals and other features (Bison 1.25, 1995).
+
+Akim Demaille rewrote the parser in Bison, and changed the back end to
+use M4 (1.50, 2002).
+
+Paul Hilfinger added GLR support (Bison 1.50, 2002).
+
+Joel E. Denny contributed canonical-LR support, and invented and added
+IELR and LAC (Lookahead Correction) support (Bison 2.5, 2011).
+
+Paolo Bonzini contributed Java support (Bison 2.4, 2008).
+
+Alex Rozenman added named reference support (Bison 2.5, 2011).
+
+Paul Eggert fixed a million portability issues, arbitrary limitations,
+and nasty bugs.
+
+-----
+
+Copyright (C) 1998-2012 Free Software Foundation, Inc.
+
+This file is part of Bison, the GNU Compiler Compiler.
+
+This program 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, either version 3 of the License, or
+(at your option) any later version.
+
+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.
+
+You should have received a copy of the GNU General Public License
+along with this program. If not, see <http://www.gnu.org/licenses/>.