Add label for licenses used, in Settings

desktop/onionshare/resources/locale/en.json

@@ -99,6 +99,7 @@
     "gui_settings_button_help": "Help",
     "gui_settings_version_label": "You are using OnionShare {}",
     "gui_settings_help_label": "Need help? See <a href='https://docs.onionshare.org'>docs.onionshare.org</a>",
+    "gui_settings_license_label": "OnionShare is licensed under the GPL v3.<br>Third-party licenses can be viewed here:<br><a href='https://github.com/onionshare/onionshare/tree/main/licenses'>https://github.com/onionshare/onionshare/tree/main/licenses</a>",
     "settings_test_success": "Connected to the Tor controller.\n\nTor version: {}\nSupports ephemeral onion services: {}.\nSupports client authentication: {}.\nSupports next-gen .onion addresses: {}.",
     "connecting_to_tor": "Connecting to the Tor network",
     "update_available": "New OnionShare out. <a href='{}'>Click here</a> to get it.<br><br>You are using {} and the latest is {}.",

desktop/onionshare/settings_tab.py

@@ -126,6 +126,11 @@ class SettingsTab(QtWidgets.QWidget):
         help_label.setTextInteractionFlags(QtCore.Qt.TextBrowserInteraction)
         help_label.setOpenExternalLinks(True)
 
+        license_label = QtWidgets.QLabel(strings._("gui_settings_license_label"))
+        license_label.setAlignment(QtCore.Qt.AlignHCenter)
+        license_label.setTextInteractionFlags(QtCore.Qt.TextBrowserInteraction)
+        license_label.setOpenExternalLinks(True)
+
         # Buttons
         self.save_button = QtWidgets.QPushButton(strings._("gui_settings_button_save"))
         self.save_button.clicked.connect(self.save_clicked)
@@ -146,6 +151,8 @@ class SettingsTab(QtWidgets.QWidget):
         layout.addWidget(version_label)
         layout.addWidget(help_label)
         layout.addSpacing(20)
+        layout.addWidget(license_label)
+        layout.addSpacing(20)
         layout.addLayout(buttons_layout)
         layout.addStretch()