Yes. I wanted to maintain the original functionality of the plug and add various Optware packages including Firefly. You'll need to know a bit about Unix/Linux and you'll need a flash drive to put Optware on (it doesn't have to be large, just large enough for packages you want). Alternatively I believe you could partition a bit of a hard drive for Optware. Most of what you'll need is here: http://www.nslu2-linux.org/wiki/Main/PlugComputers

Basically you prep the flash drive by formating it as a linux partition and an ext2/ext3 file system. Mount it and install ipkg and go.