The port was developed by Mythic Entertainment using the emulation technology seen in Elite Systems Group's C64: Elite Collection. The iOS iteration of Ultima IV includes digital copies of the manual and other documents found in the game's original 1985 release, as well as a comprehensive walkthrough and new player guide courtesy GameFAQs. Most helpfully, Ultima IV: C64 automatically saves player progress whenever the game is closed.
Ultima IV: C64 is an utterly free download, with no microtransactions to speak of. Simply download Ultima IV: C64 and it's yours.