Unfortunately, the SecureROM vulnerability that gala exploits was patched in the ROMs shipped with the 4s. Therefore, gala won't work out-of-the-box with the 4s.

However, a newer boot ROM exploit, checkm8, has become well-known in the intervening years. The A5 (that the 4s ships) is vulnerable to checkm8, which means that it'd certainly be possible to add support for this exploit chain to a project like gala!