Added GPL notifications at the top of each file, and made it clear that contributors must agree with it too.

license.txt

@@ -1,4 +1,4 @@
-Copyright (C) 2014 Dalton Nell
+Copyright (C) 2014 Dalton Nell, Slop Contributors (https://github.com/naelstrof/slop/graphs/contributors)
 
 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

main.cpp

@@ -1,3 +1,22 @@
+/* main.cpp
+ *
+ * Copyright (C) 2014: Dalton Nell, Slop Contributors (https://github.com/naelstrof/slop/graphs/contributors).
+ *
+ * This file is part of Slop.
+ *
+ * Slop 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.
+ *
+ * Slop 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 Slop.  If not, see <http://www.gnu.org/licenses/>.
+ */
 #include <unistd.h>
 #include <cstdio>
 #include "x.hpp"

rectangle.cpp

@@ -1,3 +1,22 @@
+/* rectangle.cpp: Handles creating rectangles on the screen.
+ *
+ * Copyright (C) 2014: Dalton Nell, Slop Contributors (https://github.com/naelstrof/slop/graphs/contributors).
+ *
+ * This file is part of Slop.
+ *
+ * Slop 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.
+ *
+ * Slop 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 Slop.  If not, see <http://www.gnu.org/licenses/>.
+ */
 #include "rectangle.hpp"
 
 static Bool isDestroyNotify( Display* dpy, XEvent* ev, XPointer win ) {

rectangle.hpp

@@ -1,4 +1,22 @@
-// rectangle.hpp: handles creating rectangles on screen.
+/* rectangle.hpp: Handles creating rectangles on the screen.
+ *
+ * Copyright (C) 2014: Dalton Nell, Slop Contributors (https://github.com/naelstrof/slop/graphs/contributors).
+ *
+ * This file is part of Slop.
+ *
+ * Slop 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.
+ *
+ * Slop 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 Slop.  If not, see <http://www.gnu.org/licenses/>.
+ */
 
 #ifndef IS_RECTANGLE_H_
 #define IS_RECTANGLE_H_

x.cpp

@@ -1,3 +1,22 @@
+/* x.cpp: Handles starting and managing X.
+ *
+ * Copyright (C) 2014: Dalton Nell, Slop Contributors (https://github.com/naelstrof/slop/graphs/contributors).
+ *
+ * This file is part of Slop.
+ *
+ * Slop 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.
+ *
+ * Slop 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 Slop.  If not, see <http://www.gnu.org/licenses/>.
+ */
 #include "x.hpp"
 
 slop::XEngine* xengine = new slop::XEngine();

x.hpp

@@ -1,4 +1,22 @@
-// x.hpp: handles starting and managing X
+/* x.hpp: Handles starting and managing X.
+ *
+ * Copyright (C) 2014: Dalton Nell, Slop Contributors (https://github.com/naelstrof/slop/graphs/contributors).
+ *
+ * This file is part of Slop.
+ *
+ * Slop 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.
+ *
+ * Slop 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 Slop.  If not, see <http://www.gnu.org/licenses/>.
+ */
 
 #ifndef IS_X_H_
 #define IS_X_H_