What does this do?

Its from a setup script.

wget http://malus.exotica.org.uk/~buzz/pi/sdl/sdl1/deb/rpi2/libsdl1.2debian_1.2.15-8rpi_armhf.deb
wget http://malus.exotica.org.uk/~buzz/pi/sdl/sdl2/libsdl2_2.0.3_armhf.deb

sudo dpkg -i libsdl*

sudo apt-mark hold libsdl1.2debian
sudo apt-mark hold libsdl2

Looking up libsdl it seems its a low level hook. And it looks like they are downloading a custom version from some shady website and telling it not to overwrite on an automatic update. I cant get into the files and see exactly what it does, it seems to be compiled. I dont see the reason for installing this either.

Your description of what the commands are doing sounds accurate, I don’t know if I’d describe the title as shady though.

Looks like source files are here so you could compile yourself

There is also a readme that points you to GitHub so you could see the changes made there
GitHub - joolswills/sdl1: SDL 1 with rpi fixes / dispmanx

I originally went to malus.exotica.org and it seemed shady. I forgot the .uk and it seems better. Thanks for the tips!