S/he was talking about adding chat to one of his/her sites(or customer's sites) using conversejs[0] which is indeed opensource.

[0]-https://conversejs.org/

the website i had to add it to is closed-source, but as someone below indicated, converse.js is open source. the actual code base of converse.js isnt bad - but no one was responsive on github as of a few months ago - and that was a huge problem