Sony has removed the $99 fee for anyone wanting to become a PS Mobile(PSM) developer, PSM games are released for the PS Vita and certified devices, this is not to be confused as a PS Vita dev account, which is totally different, here is a quote from the source:
We are looking forward seeing your exciting ideas become reality and having fun developing together.
To help out all the talent out there we thought it would be better to waive the publisher license fee. So we did.
To obtain a PSM Publisher License, please register or sign in to: https://psm.playstation.net/
Start date: 8th May 2013
End date: 2nd September 2013 (The duration may vary.)