Arachnophobia: Getting the macro keys on the Razer BlackWidow to work on linux

I bought the Razer BlackWidow for the hardware, not for Razer’s Synapse software or all the joys that it offers (Google suggest for searchers entering Razer Synapse? “Razer Synapse sucks”) Which meant that I was perfectly content not to use any of the special function keys on the keyboard. However the thought hit me that I had five Firefox profiles (yes, I prefer not to do my banking in the browser I watch smut in. There. Happy?) and there were five macro keys sitting in a row, not being used. 1+1=?