Clarify licenses

- add license headers to everything
- convert a few files from public domain or LGPL2.1+ to GPL2+
- some archaeology to clarify which files are from which library

19 files changed, 37 insertions, 18 deletions

diff --git a/src/debug/CMakeLists.txt b/src/debug/CMakeLists.txt
index 5c0354fce..954df1f33 100644
--- a/src/debug/CMakeLists.txt
+++ b/src/debug/CMakeLists.txt
@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
 
 set(debug_SRC
 	demangle.cpp
diff --git a/src/debug/demangle.cpp b/src/debug/demangle.cpp
index a5f868a76..28b5d26d4 100644
--- a/src/debug/demangle.cpp
+++ b/src/debug/demangle.cpp
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Inkscape::Debug::demangle - demangle C++ symbol names
  *
@@ -6,7 +7,7 @@
  *
  * Copyright (C) 2006 MenTaLguY
  *
- * Released under GNU GPL, read the file 'COPYING' for more information
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
  */
 
 #include <cstdio>
diff --git a/src/debug/demangle.h b/src/debug/demangle.h
index c5e160caa..95042446f 100644
--- a/src/debug/demangle.h
+++ b/src/debug/demangle.h
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Inkscape::Debug::demangle - demangle C++ symbol names
  *
@@ -6,7 +7,7 @@
  *
  * Copyright (C) 2006 MenTaLguY
  *
- * Released under GNU GPL, read the file 'COPYING' for more information
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
  */
 
 #ifndef SEEN_INKSCAPE_DEBUG_DEMANGLE_H
diff --git a/src/debug/event-tracker.h b/src/debug/event-tracker.h
index 8a2e6242a..e70e2adf0 100644
--- a/src/debug/event-tracker.h
+++ b/src/debug/event-tracker.h
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Inkscape::Debug::EventTracker - semi-automatically track event lifetimes
  *
@@ -6,7 +7,7 @@
  *
  * Copyright (C) 2005 MenTaLguY
  *
- * Released under GNU GPL, read the file 'COPYING' for more information
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
  */
 
 #ifndef SEEN_INKSCAPE_DEBUG_EVENT_TRACKER_H
diff --git a/src/debug/event.h b/src/debug/event.h
index 1ddcb8b55..e9fa5ae2e 100644
--- a/src/debug/event.h
+++ b/src/debug/event.h
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Inkscape::Debug::Event - event for debug tracing
  *
@@ -6,7 +7,7 @@
  *
  * Copyright (C) 2005 MenTaLguY
  *
- * Released under GNU GPL, read the file 'COPYING' for more information
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
  */
 
 #ifndef SEEN_INKSCAPE_DEBUG_EVENT_H
diff --git a/src/debug/gc-heap.h b/src/debug/gc-heap.h
index 88de2b7e8..155e13eb1 100644
--- a/src/debug/gc-heap.h
+++ b/src/debug/gc-heap.h
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Inkscape::Debug::GCHeap - heap statistics for libgc heap
  *
@@ -6,7 +7,7 @@
  *
  * Copyright (C) 2004 MenTaLguY
  *
- * Released under GNU GPL, read the file 'COPYING' for more information
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
  */
 
 #ifndef SEEN_INKSCAPE_DEBUG_GC_HEAP_H
diff --git a/src/debug/gdk-event-latency-tracker.cpp b/src/debug/gdk-event-latency-tracker.cpp
index 4679f05f1..57d3e1f25 100644
--- a/src/debug/gdk-event-latency-tracker.cpp
+++ b/src/debug/gdk-event-latency-tracker.cpp
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Inkscape::Debug::GdkEventLatencyTracker - tracks backlog of GDK events
  *
@@ -6,7 +7,7 @@
  *
  * Copyright (C) 2008 MenTaLguY
  *
- * Released under GNU GPL, read the file 'COPYING' for more information
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
  */
 
 #include <gdk/gdk.h>
diff --git a/src/debug/gdk-event-latency-tracker.h b/src/debug/gdk-event-latency-tracker.h
index 75a861a40..9c1cd1fb3 100644
--- a/src/debug/gdk-event-latency-tracker.h
+++ b/src/debug/gdk-event-latency-tracker.h
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Inkscape::Debug::GdkEventLatencyTracker - tracks backlog of GDK events
  *
@@ -6,7 +7,7 @@
  *
  * Copyright (C) 2008 MenTaLguY
  *
- * Released under GNU GPL, read the file 'COPYING' for more information
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
  */
 
 #ifndef SEEN_INKSCAPE_DEBUG_GDK_EVENT_LATENCY_TRACKER_H
diff --git a/src/debug/heap.cpp b/src/debug/heap.cpp
index d543a18f6..ce9cacfa9 100644
--- a/src/debug/heap.cpp
+++ b/src/debug/heap.cpp
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Inkscape::Debug::Heap - interface for gathering heap statistics
  *
@@ -6,7 +7,7 @@
  *
  * Copyright (C) 2005 MenTaLguY
  *
- * Released under GNU GPL, read the file 'COPYING' for more information
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
  */
 
 #include "inkgc/gc-alloc.h"
diff --git a/src/debug/heap.h b/src/debug/heap.h
index 959578893..72aae1603 100644
--- a/src/debug/heap.h
+++ b/src/debug/heap.h
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Inkscape::Debug::Heap - interface for gathering heap statistics
  *
@@ -6,7 +7,7 @@
  *
  * Copyright (C) 2005 MenTaLguY
  *
- * Released under GNU GPL, read the file 'COPYING' for more information
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
  */
 
 #ifndef SEEN_INKSCAPE_DEBUG_HEAP_H
diff --git a/src/debug/log-display-config.cpp b/src/debug/log-display-config.cpp
index a2e07e207..e96802847 100644
--- a/src/debug/log-display-config.cpp
+++ b/src/debug/log-display-config.cpp
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Inkscape::Debug::log_display_config - log display configuration
  *
@@ -6,7 +7,7 @@
  *
  * Copyright (C) 2007 MenTaLguY
  *
- * Released under GNU GPL, read the file 'COPYING' for more information
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
  */
 
 #include <iostream>
diff --git a/src/debug/log-display-config.h b/src/debug/log-display-config.h
index 6a598ac0f..9adef3347 100644
--- a/src/debug/log-display-config.h
+++ b/src/debug/log-display-config.h
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Inkscape::Debug::log_display_config - log display configuration
  *
@@ -6,7 +7,7 @@
  *
  * Copyright (C) 2007 MenTaLguY
  *
- * Released under GNU GPL, read the file 'COPYING' for more information
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
  */
 
 #ifndef SEEN_INKSCAPE_DEBUG_LOG_DISPLAY_CONFIG_H
diff --git a/src/debug/logger.cpp b/src/debug/logger.cpp
index e89d895b8..742ad6e58 100644
--- a/src/debug/logger.cpp
+++ b/src/debug/logger.cpp
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Inkscape::Debug::Logger - debug logging facility
  *
@@ -6,7 +7,7 @@
  *
  * Copyright (C) 2005 MenTaLguY
  *
- * Released under GNU GPL, read the file 'COPYING' for more information
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
  */
 
 #include <fstream>
diff --git a/src/debug/logger.h b/src/debug/logger.h
index b5970e1ba..ab6c82641 100644
--- a/src/debug/logger.h
+++ b/src/debug/logger.h
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Inkscape::Debug::Logger - debug logging facility
  *
@@ -6,7 +7,7 @@
  *
  * Copyright (C) 2005 MenTaLguY
  *
- * Released under GNU GPL, read the file 'COPYING' for more information
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
  */
 
 #ifndef SEEN_INKSCAPE_DEBUG_LOGGER_H
diff --git a/src/debug/simple-event.h b/src/debug/simple-event.h
index 7870ca0d1..7dc706fe7 100644
--- a/src/debug/simple-event.h
+++ b/src/debug/simple-event.h
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Inkscape::Debug::SimpleEvent - trivial implementation of Debug::Event
  *
@@ -6,7 +7,7 @@
  *
  * Copyright (C) 2005 MenTaLguY
  *
- * Released under GNU GPL, read the file 'COPYING' for more information
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
  */
 
 #ifndef SEEN_INKSCAPE_DEBUG_SIMPLE_EVENT_H
diff --git a/src/debug/sysv-heap.cpp b/src/debug/sysv-heap.cpp
index 2731a931e..41455e62a 100644
--- a/src/debug/sysv-heap.cpp
+++ b/src/debug/sysv-heap.cpp
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Inkscape::Debug::SysVHeap - malloc() statistics via System V interface
  *
@@ -6,7 +7,7 @@
  *
  * Copyright (C) 2005 MenTaLguY
  *
- * Released under GNU GPL, read the file 'COPYING' for more information
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
  */
 
 #ifdef HAVE_CONFIG_H
diff --git a/src/debug/sysv-heap.h b/src/debug/sysv-heap.h
index 6f95b74c4..3829eb11d 100644
--- a/src/debug/sysv-heap.h
+++ b/src/debug/sysv-heap.h
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Inkscape::Debug::SysVHeap - malloc() statistics via System V interface
  *
@@ -6,7 +7,7 @@
  *
  * Copyright (C) 2005 MenTaLguY
  *
- * Released under GNU GPL, read the file 'COPYING' for more information
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
  */
 
 #ifndef SEEN_INKSCAPE_DEBUG_SYSV_HEAP_H
diff --git a/src/debug/timestamp.cpp b/src/debug/timestamp.cpp
index cdd47e881..e22f8dede 100644
--- a/src/debug/timestamp.cpp
+++ b/src/debug/timestamp.cpp
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Inkscape::Debug::SimpleEvent - trivial implementation of Debug::Event
  *
@@ -6,7 +7,7 @@
  *
  * Copyright (C) 2007 MenTaLguY
  *
- * Released under GNU GPL, read the file 'COPYING' for more information
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
  */
 
 
diff --git a/src/debug/timestamp.h b/src/debug/timestamp.h
index c145ffbc9..281c31b4c 100644
--- a/src/debug/timestamp.h
+++ b/src/debug/timestamp.h
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Inkscape::Debug::timestamp - timestamp strings
  *
@@ -6,7 +7,7 @@
  *
  * Copyright (C) 2007 MenTaLguY
  *
- * Released under GNU GPL, read the file 'COPYING' for more information
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
  */
 
 #ifndef SEEN_INKSCAPE_DEBUG_TIMESTAMP_H