RoActDat is a plugin (or app) that will block sony (or anyone else) from deactivating your PSVita.
Just run the app and tm0 will be remounted Read/Only (BUT ONLY UNTIL NEXT REBOOT)
Add RoActDat.skprx to *KERNEL in config.txt, to make tm0: be remounted as read-only whenever henkaku loads
(Which if you use enso is at bootup)
To test if its working just try to copy a file to tm0 it should throw error 0x8001001E in vitashell.
!Works on 3.65 and 3.68!