Just because they send someone an email saying they "may be a good fit" doesn't mean they are offering them the job. The person would still have to go through the whole formal interviewing and hiring process.
This might not be related to the PS3, but more toward their upcoming Android phone. For those who don't know, Koush works on ClockworkMod, a flashable android recovery that allows users to backup and flash ROMS on their android devices, among other things. I can see it as a move to stop piracy on the phone if they release games or whatever on it.
This guy is a very skilled programmer and its possible he had applied for a different position, and with Sony's move to drop there new game platform to Android hence e-mailing him with a different job title offer.
This has nothing to do with the ps3 aside from someone very public to the android scene getting recruited by sony and telling everyone about it.
PSFreedom is what he made for the ps3 the Jailbreaking app for the android platform.