I'd like to announce that SaaSHub has a simple public API now. There are two endpoints as of now. In general, that should be sufficient for some basic integrations; however, the API could be extended in the future.
The API is free and, all you need is a SaaSHub user account.
In essence, you can get all the alternatives to a given product through a simple GET query
You can find the relevant docs here https://www.saashub.com/site/api
If you decide to use the API and need any help or have an idea how to improve it, please don't hesitate to ping me. Thanks!