Add source-available license (no redistribution / publishing)

Code is publicly viewable and forkable for personal use, but redistribution,
publishing (any app store/release), and commercial use are prohibited — all
publishing rights reserved to the copyright holder. Combined with the private
release signing key, this keeps the app exclusively the owner's to publish.

LICENSE

@@ -0,0 +1,40 @@
+SyncFlow Source-Available License
+Copyright (c) 2026 Amir Khodak. All rights reserved.
+
+This is NOT an OSI-approved open-source license. The source code is made
+publicly viewable ("source-available"), but the rights granted are limited as
+described below. Where this license is silent, all rights are reserved.
+
+1. DEFINITIONS
+   "Software" means the SyncFlow source code, assets, and documentation in this
+   repository. "You" means anyone other than the copyright holder.
+
+2. WHAT YOU MAY DO
+   a. View, read, and study the Software.
+   b. Clone or fork the repository for your own private, personal,
+      non-commercial use and experimentation.
+   c. Build the Software from source and run it on devices you personally own.
+   d. Submit contributions (pull requests) back to this repository; by doing so
+      you license your contribution to the copyright holder under these terms.
+
+3. WHAT YOU MAY NOT DO (without the copyright holder's prior written permission)
+   a. Redistribute, publish, or make available the Software or any derivative
+      work — in source or binary/APK form — to any third party or app store
+      (including but not limited to Google Play, F-Droid, Amazon Appstore,
+      Gitea/GitHub releases, or any website).
+   b. Use the Software, in whole or in part, for any commercial purpose.
+   c. Sell, sublicense, rent, or offer the Software as a service.
+   d. Use the names, app identity ("SyncFlow"), package identifier
+      ("com.syncflow"), logos, or signing keys of the original work.
+   e. Remove or alter this license or the copyright notice.
+
+4. RESERVED RIGHTS
+   All publishing and distribution rights are reserved exclusively to the
+   copyright holder. Only the copyright holder may publish official builds.
+
+5. NO WARRANTY
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE FOR ANY CLAIM,
+   DAMAGES, OR OTHER LIABILITY ARISING FROM THE SOFTWARE OR ITS USE.
+
+To request permission for anything in section 3, contact the copyright holder.

README.md

@@ -40,3 +40,10 @@ Native Android file sync app — sync any folder to WebDAV, SFTP, Nextcloud, own
 
 - Android 8.0+ (API 26)
 - Storage permission (or SAF picker) for local folder access
+
+## License
+
+SyncFlow is **source-available, not open-source** — see [LICENSE](LICENSE).
+You may read, study, and fork it for personal, non-commercial use, but
+**redistributing or publishing the app (source or APK) is not permitted**.
+Only the copyright holder publishes official, signed builds.