From the X Terminal:

root
wget http://alephzain.klutsh.com/default_payload_3_41.bin [only needs to done once, omit this line next time]
n900-enable-jailbreak.sh
cat default_payload_3_41.bin > /proc/psfreedom/payload
[Jailbreak your PS3 here]
n900-disable-jailbreak.sh

Or replace the file in /opt/psfreedom/payloads/ though I am not sure which one to replace, I don't know which one the gui uses.

And yes, I still warn you, you most likely will get banned sooner or later and there's nothing at that point the devs can do about it. It works for now, though.