Apply the GPLv3 license

Copyright disclaimer and copyright note are prepending to a every source
file.

Add license section in the `README.md` file.

Create the LICENSE` file with license information.

Signed-off-by: Alexey Gavrilov <alexey.gavrilov@mail.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/arch/x86/io/VGADisplay.cpp b/arch/x86/io/VGADisplay.cpp
index 7246102..50fd4b7 100644
--- a/arch/x86/io/VGADisplay.cpp
+++ b/arch/x86/io/VGADisplay.cpp
@@ -1,3 +1,21 @@
+/**
+ * Copyright (c) 2026 Alexey Gavrilov <alexey.gavrilov@mail.com>
+ *
+ * This file is part of ObjectiveOS.
+ *
+ * ObjectiveOS 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.
+ *
+ * ObjectiveOS 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
+ * ObjectiveOS. If not, see <https://www.gnu.org/licenses/>. 
+ */
+
 #include "VGADisplay.h"
 
 VGADisplay out::display;