# Additional permission for Polar's BLE SDK

Train's app (`apps/train/halkyon_train_flutter`) is under the GNU Affero General Public
License, version 3 or any later version (`LICENSE`). Its Android build links Polar
Electro Oy's Polar BLE SDK for the Polar Loop (ADR 0030, D34, D36), which is under
Polar's *Software Development Kit Limited License Agreement*, not a free licence
(`assets/licences/Polar_SDK_License.txt`). For that, its licensors add this permission,
under section 7 of the GNU AGPL version 3:

> Additional permission under GNU AGPL version 3 section 7
>
> If you modify this Program, or any covered work, by linking or combining it with the
> Polar BLE SDK of Polar Electro Oy (or a modified version of that library), containing
> parts covered by the terms of Polar's Software Development Kit Limited License
> Agreement, the licensors of this Program grant you additional permission to convey the
> resulting work. Corresponding Source for a non-source form of such a combination
> shall include the source code for the parts of this Program used, but not for the
> parts of the Polar BLE SDK used.

The SDK's own terms still bind whoever conveys it: Polar's agreement allows its object
code to be distributed only together with an app and to move data between Polar's
devices and that app, and Polar may end it.