Oralayerextractor extracts individual layers from an ORA file, in a different way from MyPaint's 'Multiple PNG' export. MyPaint's Multiple PNG export results in N PNGs each sized to match the image, named numerically. Oralayerextractor results in N PNGs each sized to match individual layer content, named in accordance with layer name.
Oralayerextractor is useful, for example, when you do one drawing on each layer, and care about extracting the individual drawings but not about their position in the overall image. It is also useful when the layer name is important information.
For a comparison of MyPaint Multiple-PNG export and Oralayerextractor on the same document, visit these links: