Jellyfin is open sourced and supported by donations. I've used it for around a year and I can confirm there have been no fees, tracking, or anything else.
I am going to downvote you because you put zero effort in understanding that they are offering only the software as free software, not hardware or streaming in any form
It's a FOSS application. Software that users deploy on their own hardware to host videos that they store themselves and make them available for clients to view either on LAN or the internet. It's not something like a Youtube alternative that would need to pay hosting costs for petabytes of (pirated) media, the only costs Jellyfin's developers incur are the costs of labor (coding, graphic design, debugging, etc)
Jellyfin was forked from Emby in response to exactly those things several years ago. It's a reliable, well supported, actively developed product that replaced Plex for me with ease.
I'm guessing you don't have much experience with FOSS software. It's volunteer driven, with a set of passionate maintainors at the helm. Much like Linux.