How do you cut open a gourd? There many ways to do it, but the best way, by far, is by using a crafter's jigsaw with a specialized foot designed exclusively for use when cutting gourds.
Designed and sold exclusively by Welburn Gourd Farm, the "Gourd Foot" has helped thousands of gourd artists make simple as well as complex cuts on their gourds.
Link to Proxxon Jigsaw with the Gourd Foot:
https://welburngourdfarm.com/collections/jigsaws/products/proxxon-mini-super-jigsaw