Telekram is a Kotlin MTProto library for Telegram, supporting not only bots, but also userbots and UI clients
Telekram is licensed under LGPLv3, which means you can use it anywhere you like, but if you modify it and share this modified version (including packaging it in a JAR file), you have to provide the source of the modified version. If you embed even an unmodified version in a JAR file, you must allow users to unpack, edit, and reverse engineer the JAR file, so that they can modify the library themselves.