Clarify licenses, round 3

Revert the previous 2 commits...

The license of the examples and test programs are indeed GPLv2+ and not
LGPLv2.1+, and the SPDX identifiers were wrong.

In the time frame where the examples and test programs were using the
incorrect SPDX identifiers, the only contributor apart from myself was
Nuno Sa, who contributed the adrv9002-iiostream.c example under the
LGPLv2+ license. He gave his consent for the relicense in the following
github thread:
#924

Signed-off-by: Paul Cercueil <[email protected]>

Author: pcercuei

COPYING_GPL.txt

@@ -4,9 +4,10 @@ Library for interfacing with Linux IIO devices
 
 libiio is used to interface to the Linux Industrial Input/Output (IIO) Subsystem. The Linux IIO subsystem is intended to provide support for devices that in some sense are analog to digital or digital to analog converters (ADCs, DACs). This includes, but is not limited to ADCs, Accelerometers, Gyros, IMUs, Capacitance to Digital Converters (CDCs), Pressure Sensors, Color, Light and Proximity Sensors, Temperature Sensors, Magnetometers, DACs, DDS (Direct Digital Synthesis), PLLs (Phase Locked Loops), Variable/Programmable Gain Amplifiers (VGA, PGA), and RF transceivers. You can use libiio natively on an embedded Linux target (local mode), or use libiio to communicate remotely to that same target from a host Linux, Windows or MAC over USB or Ethernet or Serial.
 
-Although libiio was primarily developed by Analog Devices Inc., it is an active open source library, which many people have contributed to. The library is released under the GNU Lesser General Public License (LGPL), version 2.1 or (at your option) any later version. This open-source license allows anyone to use the library, on any vendors processor/FPGA/SoC, which may be controlling any vendors peripheral device (ADC, DAC, etc) either locally or remotely. This includes closed or open-source, commercial or non-commercial applications (subject to the LGPL license freedoms, obligations and restrictions).
+Although libiio was primarily developed by Analog Devices Inc., it is an active open source library, which many people have contributed to. The library is released under the GNU Lesser General Public License (LGPL), version 2.1 or (at your option) any later version, this open-source license allows anyone to use the library, on any vendors processor/FPGA/SoC, which may be controlling any vendors peripheral device (ADC, DAC, etc) either locally or remotely. This includes closed or open-source, commercial or non-commercial applications (subject to the LGPL license freedoms, obligations and restrictions). The examples and test applications (sometimes referred to as the iio-utils) are released separately under the GNU General Public License (GPL) version 2.0 (at your option) any later version.
 
-Library/Tests/Examples/IIOD License : [![Libiio License](https://img.shields.io/badge/license-LGPL2+-blue.svg)](https://github.com/analogdevicesinc/libiio/blob/master/COPYING.txt)
+Library License : [![Library License](https://img.shields.io/badge/license-LGPL2+-blue.svg)](https://github.com/analogdevicesinc/libiio/blob/master/COPYING.txt)
+Tests/Examples License : [![Application License](https://img.shields.io/badge/license-GPL2+-blue.svg)](https://github.com/analogdevicesinc/libiio/blob/master/COPYING_GPL.txt)
 Latest Release : [![GitHub release](https://img.shields.io/github/release/analogdevicesinc/libiio.svg)](https://github.com/analogdevicesinc/libiio/releases/latest)
 Downloads :  [![Github All Releases](https://img.shields.io/github/downloads/analogdevicesinc/libiio/total.svg)](https://github.com/analogdevicesinc/libiio/releases/latest)
 

README.md

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: LGPL-2.1-or-later
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * libiio - AD9361 IIO streaming example
  *

examples/ad9361-iiostream.c

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: LGPL-2.1-or-later
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * libiio - AD9371 IIO streaming example
  *

examples/ad9371-iiostream.c

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: LGPL-2.1-or-later
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * libiio - Library for interfacing industrial I/O (IIO) devices
  *

examples/adrv9002-iiostream.c

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: LGPL-2.1-or-later
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * libiio - ADRV9009 IIO streaming example
  *

examples/adrv9009-iiostream.c

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: LGPL-2.1-or-later
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * libiio - Dummy IIO streaming example
  *

examples/dummy-iiostream.c

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: LGPL-2.1-or-later
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * libiio - Library for interfacing industrial I/O (IIO) devices
  *

examples/iio-monitor.c

@@ -1,4 +1,4 @@
-# SPDX-License-Identifier: LGPL-2.1+
+# SPDX-License-Identifier: LGPL-2.1-or-later
 #
 # iiod - Systemd init script
 #

iiod/init/iiod.service.cmakein

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: LGPL-2.1-or-later
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * iio_adi_dac_overflow_test - part of the IIO utilities
  *