Hey! To answer your question, the jam is generally horror themed and it's expected games will follow the spirit of the jam, but the optional theme of the jam is 'machine' - which can be interpreted however jammers like!
- SCREAM CATALOGUE
Viewing post in Hello . . I love horror games, what are the rules . .
You can find a list of the past jams (and browse through their entries) here https://screamcatalogue.itch.io/.
As far as YouTube videos, yes! Here are two streams by the hosts:
Scream Stream 2018 https://www.youtube.com/watch?v=QPd3WJS27N0
Scream Empire https://www.youtube.com/watch?v=MrBcZMlIliU
And here are two I did.
Scream Solstice: https://www.youtube.com/watch?v=drAC9dnLklU&t=1s
Scream Stream 2019: https://www.youtube.com/playlist?list=PLFJ0F3UuyF_HH4DFQ__x7cXFSA-T7-jsw (This was a three-parter due to how many entries there were. That's a horror jam on Halloween for you.)
There may be others, but they haven't been posted in the Discord. Which you can find here, if you haven't joined https://discord.gg/bRN8kWu