A list of companies which list (or have listed) backtrader or for which a public usage reference exists (Professional Profile, Blog Entry, Articles, ...)
This is not any kind of endorsement, proof of work, official sanctioning (and any other disclaimer)
From a LinkedIn profile and the Rankia/Finanzas.com articles
Small shop with articles, offering services for algorithmic trading.
From blog entries, job offers ...
Listed on the website
Listed backtrader as one of the technologies used and posted a job offer in the community