Just uploaded the 0.9 Beta release of Aseprite to Internet Archive. It works on Windows XP, making a perfect pairing with RPG Maker 2003! https://archive.org/details/aseprite-0.9-win32
Since uploading this, I've found out that the official Aseprite website hosts ver. 0.9.5 still. I've been using that version as of late since it has some big fixes, but overall it works the same as 0.9