It works, but you need to make the following simple changes. In PNGImage.pas, the procedures ReadData, WriteData, FlushData, and IOCallback, should have cdecl calling conventions instead of stdcall calling conventions. So I guess all you need is the appropriate ifdef's for that. After you do that, it seems to work: I see a man and a dog, animated, and you can cast a spell on the dog, revive the dog, and remove hair, pants, and breastplate (?) from the man.

There are some warnings as well, here they are:

Code:
Compiling SDLPoxDemo.dpr
Compiling sdl.pas
Compiling sdl_image.pas
Compiling SoAoSSprite.pas
SoAoSSprite.pas(143,23) Warning: Function result does not seem to be set
SoAoSSprite.pas(150,27) Warning: Function result does not seem to be set
SoAoSSprite.pas(79,5) Note: Private field "TSoAoSSprite.Flags" is never used
SoAoSSprite.pas(80,5) Note: Private field "TSoAoSSprite.isDead" is never used
Compiling sdlcolor.pas
Compiling stringini.pas
Compiling PNGImage.pas
Compiling libpng.pas
libpng.pas(1630,30) Warning: Mixing signed expressions and longwords gives a 64bit result
libpng.pas(1636,44) Warning: Mixing signed expressions and longwords gives a 64bit result
libpng.pas(1643,30) Warning: Mixing signed expressions and longwords gives a 64bit result
libpng.pas(1649,47) Warning: Mixing signed expressions and longwords gives a 64bit result
PNGImage.pas(828,9) Warning: Symbol "png_set_gray_1_2_4_to_8" is deprecated
SDLPoxDemo.dpr(89,3) Note: Local variable "MouseX" is assigned but never used
SDLPoxDemo.dpr(90,3) Note: Local variable "MouseY" is assigned but never used
SDLPoxDemo.dpr(93,3) Note: Local variable "Header" not used
SDLPoxDemo.dpr(95,3) Note: Local variable "ChunkName" not used
SDLPoxDemo.dpr(96,3) Note: Local variable "IHDRData" not used
SDLPoxDemo.dpr(97,3) Note: Local variable "DataPointer" not used
SDLPoxDemo.dpr(98,3) Note: Local variable "CheckCRC" not used
SDLPoxDemo.dpr(45,3) Note: Local variable "FrameWidth" is assigned but never used
SDLPoxDemo.dpr(45,15) Note: Local variable "FrameHeight" is assigned but never used
Compiling resource SDLPoxDemo.res
Linking SDLPoxDemo
9489 Lines compiled, 0.7 sec