Hi Morix,
SDL is not supported by default in the TI AM335x SDK. You can try to cross-compile it, but I couldn't find anyone who has done it for the Arago Project.
Here are some useful links I found:
http://wiki.libsdl.org/FAQLinux#How_do_I_add_SDL_to_my_project.3F
http://kevino.tistory.com/entry/How-to-cross-compile-SDL-for-target-arm-board
http://forums.libsdl.org/viewtopic.php?p=8696&sid=0f7c0fef844d15f380e49e5c4ad83801
http://www.libsdl.org/tmp/SDL/README-raspberrypi.txt
http://www.libsdl.org/tmp/SDL/README-linux.txt
Best regards,
Miroslav