diff --git a/docs/licenses/README.TXT b/docs/licenses/README.TXT
index 3463a5ed7e..53d939b06e 100644
--- a/docs/licenses/README.TXT
+++ b/docs/licenses/README.TXT
@@ -11,6 +11,9 @@ The majority of original code uses a BSD-like lincese. See bsd.txt.
 The OpenGL renderer is released under the LGPL v3, except some bits
 of code that were inherited fro ZDoomGL.
 
+Some code was taken from the Eternity Engine.
+Copyright (c) James Haley, Stephen McGranahan, et al.
+
 This software is based in part on the work of the Independent JPEG Group.
 
 This software uses the 'zlib' general purpose compression library by
diff --git a/src/playsim/portal.cpp b/src/playsim/portal.cpp
index 5a9c8b3a60..5076e0a984 100644
--- a/src/playsim/portal.cpp
+++ b/src/playsim/portal.cpp
@@ -1,41 +1,28 @@
-/*
-** portals.cpp
-** Everything that has to do with portals (both of the line and sector variety)
-**
-**---------------------------------------------------------------------------
-** Copyright 2016 ZZYZX
-** Copyright 2016 Christoph Oelckers
-** All rights reserved.
-**
-** Redistribution and use in source and binary forms, with or without
-** modification, are permitted provided that the following conditions
-** are met:
-**
-** 1. Redistributions of source code must retain the above copyright
-**    notice, this list of conditions and the following disclaimer.
-** 2. Redistributions in binary form must reproduce the above copyright
-**    notice, this list of conditions and the following disclaimer in the
-**    documentation and/or other materials provided with the distribution.
-** 3. The name of the author may not be used to endorse or promote products
-**    derived from this software without specific prior written permission.
-**
-** THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
-** IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
-** OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
-** IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
-** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
-** NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
-** THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-**---------------------------------------------------------------------------
-**
-** There is no code here that is directly taken from Eternity
-** although some similarities may be inevitable because it has to
-** implement the same concepts.
-*/
-
+//
+//-----------------------------------------------------------------------------
+//
+// Copyright 2016 ZZYZX, Christoph Oelckers, et. al.
+//
+// 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/
+//
+//--------------------------------------------------------------------------
+//
+// DESCRIPTION:
+// Everything that has to do with portals
+// (both of the line and sector variety)
+//
+//-----------------------------------------------------------------------------
 
 #include "p_local.h"
 #include "p_blockmap.h"