Add license sample

CONTRIBUTING.md

@@ -22,6 +22,7 @@
         1. Create another pull request
         1. Backport pull request
         1. Pull requests that also need changes on library
+        1. Adding new files
     1. Translations
 1. Releases
     1. Types
@@ -153,6 +154,88 @@ Once both PRs are reviewed and ready to merge:
 
 With this approach the "downtime" of not building master is limited to the timestamp between merge lib PR and merging app PR, which is only limited by CI.
 
+### 6. Adding new files
+If you create a new file it needs to contain a license header. We encourage you to use the same license (AGPL3+) as we do.
+Copyright of Nextcloud GmbH is optional.
+
+Source code of library:
+```java
+ /* Nextcloud Android Library is available under MIT license
+ *
+ *   @author Your Name
+ *   Copyright (C) 2019 Your Name
+ *   Copyright (C) 2019 Nextcloud GmbH
+ *   
+ *   Permission is hereby granted, free of charge, to any person obtaining a copy
+ *   of this software and associated documentation files (the "Software"), to deal
+ *   in the Software without restriction, including without limitation the rights
+ *   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ *   copies of the Software, and to permit persons to whom the Software is
+ *   furnished to do so, subject to the following conditions:
+ *   
+ *   The above copyright notice and this permission notice shall be included in
+ *   all copies or substantial portions of the Software.
+ *   
+ *   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
+ *   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ *   MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
+ *   NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS 
+ *   BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN 
+ *   ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN 
+ *   CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ *   THE SOFTWARE.
+ *
+ */
+ ```
+
+Source code of app:
+```java
+/*
+ * Nextcloud Android client application
+ *
+ * @author Your Name
+ * Copyright (C) 2019 Your Name
+ * Copyright (C) 2019 Nextcloud GmbH
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+ ```
+
+ XML (layout) file:
+ ```xml
+<!--
+  Nextcloud Android client application
+
+  @author Your Name
+  Copyright (C) 2019 Your Name
+  Copyright (C) 2019 Nextcloud GmbH
+
+  This program is free software: you can redistribute it and/or modify
+  it under the terms of the GNU Affero General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  This program 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 Affero General Public License for more details.
+
+  You should have received a copy of the GNU Affero General Public License
+  along with this program. If not, see <https://www.gnu.org/licenses/>.
+-->
+```
+
 ## Translations
 We manage translations via [Transifex](https://www.transifex.com/nextcloud/nextcloud/android/). So just request joining the translation team for Android on the site and start translating. All translations will then be automatically pushed to this repository, there is no need for any pull request for translations.