One day ago, Mr idumpvitastuff at reddit released Hidden Applications for PS Vita 3.63, which allows you to launch Package installer and Sign Up For PSN. Package installer will refuse to start on retail Vitas, while Sign Up For PSN enables Account Switching.
idumpvitastuff gives a tutorial about installing it:
0.1 Download Hidden Applications (CreateBackup.zip)
1. Download VitaIMGTools for your OS
2. Obtain your CMA Key From here just enter your AID (the random letters and numbers where your CMA backups are stored.) and it will give you the key
3. put the PSVIMGTools in the same folder you extracted CreateBackup.zip
4. Run the BuildScript for your OS. either the win32 one of osx/linux depending on what you have
5. Paste/Enter your CMA Key and press enter
6. Copy the “HIDENAPPS” folder into your CMA Backups/APP Folder
7 Refresh CMA Database, and restore backup to your vita