I can get to the former, but not http://deb.wp.puri.sm/pureos/.
For Meltdown, I believed the last paragraph on the webpage you provided: “All new laptop shipments include Meltdown and Spectre patches.” I received mine several months afterwards, and I have not reinstalled PureOS. In any case, the Linux kernel has been updated since these instructions. If you know otherwise… 
As for the original firmware script, kakaroto is the author, so he would be the one to chime in.