YouTube Downloader uses FFmpeg licensed under the
LGPLv3 and its source can be downloaded
here. FFmpeg uses the
LAME mp3 library licensed under the
LGPLv2.0 and its source code
can be downloaded here.
FFmpeg also uses the opencore-amr library licensed
under the Apache License v2.0 and its source code can be downloaded
here.
YouTube Downloader uses librtmp licensed under the LGPLv2.0 and its source can be downloaded here.
YouTube Downloader uses OpenSSL under an Apache-style licence and its source can be downloaded here.