Some may be interested in this demo of the animation features added to DPaint3 (demoed by Dan Silva, the main author):

https://www.youtube.com/watch?v=WjIQO1MjV2w

Also, looks like the source code for DPaint1 has been made available:

https://computerhistory.org/blog/electronic-arts-deluxepaint...

https://github.com/historicalsource/DeluxePaint

Written in C!

I always thought it was written in ASM.