You are dealing with two different animals. The AY0438 is for 
conventional multi-segment LCDs such as simple 7 segment types. In a 
hobbyist situation it is far less likely to be encountered.

The HD44780 on the other hand is used in just about every text type 
dot-matrix LCD display around! Well, most of them anyway. Thus the 
HD44780 (and it's compatible types) is a very common interfacing need 
hence the number of libraries you have found for it. The same holds 
true for just about any micro you care to name - you will find 
HD44780 code in many guises.

John

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