The script wouldn't be able to detect what languages are available to download, so the users have to specify that they want to download the "en" version, for example.
I see this was never commented on. Could be useful and not too invasive to change but out of scope for me currently. Happy to review pull requests though.
For example, the video of this course https://www.coursera.org/course/calvin is in french, but it has 2 subtitles: french & english.
The published link on the course page (https://class.coursera.org/calvin-001/lecture/index) is only french subtitle, for example : https://class.coursera.org/calvin-001/lecture/subtitles?q=55_fr&format=srt . The english version of that subtitle is just to replace "fr" with "en" https://class.coursera.org/calvin-001/lecture/subtitles?q=55_en&format=srt
The script wouldn't be able to detect what languages are available to download, so the users have to specify that they want to download the "en" version, for example.