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DL: language lessons vs Busuu: catalog facts
DL: language lessons	Busuu
Free The client is free and open source under GPL-3.0; Duolingo's own plans apply.	Freemium Free to start, with a paid subscription for full access.
Linux	Android, iOS, Web
Dedicated window for Duolingo on Linux Blocks common trackers	Feedback from a community of native speakers Pronunciation feedback in speaking practice
Unofficial and not affiliated with Duolingo Only wraps the web app, so it needs an internet connection to Duolingo	Full course access requires payment Proprietary service that needs an account
Downloadable app	Downloadable app, Web application
Open source	Closed source
License: GPL-3.0	License not stated
Not stated if an account is needed	Account needed
Not stated if it works offline	Not stated if it works offline
Official website Full listing and sources Checked October 1, 2026	Official website Full listing and sources Checked September 23, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.