For macronutrients and android there is waistline¹(available on fdroid and google app stores). It's pretty much what you asked for, open source and it uses OpenFoodFacts. It's more focused than myfitnesspal, but very usable and I think eating habits are too intimate to share with a company. Plus with myfitnesspal I feel like I'm working for the company when I add products to the database, not so with OpenFoodFacts.

[1] https://github.com/davidhealey/waistline