Updated license (#3)

Co-authored-by: Mykyta Solomko <sev@nix.org.ua>
Reviewed-on: https://code.nix.org.ua/ansible/module-slapt-get/pulls/3
Co-authored-by: Mykyta Solomko <sev@no-reply.code.nix.org.ua>
Co-committed-by: Mykyta Solomko <sev@no-reply.code.nix.org.ua>

LICENSE.txt

@@ -1,29 +1,16 @@
-Copyright 2018 Mykyta Solomko, Kyiv, Ukraine, <sev@nix.org.ua>
-All rights reserved.
+(c) 2017-2021, Mykyta Solomko
+Written by Mykyta Solomko <sev@nix.org.ua>
 
-1. Redistributions of source code must retain the above copyright
-notice, this list of conditions and the following disclaimer.
+This module 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.
 
-2. The origin of this software must not be misrepresented; you must
-not claim that you wrote the original software.  If you use this
-software in a product, an acknowledgment in the product
-documentation would be appreciated but is not required.
+This software 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.
 
-3. Altered source versions must be plainly marked as such, and must
-not be misrepresented as being the original software.
+You should have received a copy of the GNU General Public License
+along with this software.  If not, see <http://www.gnu.org/licenses/>.
 
-4. 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.