I have questions about the contained vitamin D in NORSAN Vegan?

A daily dose, 1 teaspoon/5 ml, contains 2,000 mg of Omega-3 and 20µg of vitamin D3/800 IU.

The vitamin D contained in Omega-3 Vegan is vegan. The vegan vitamin D is obtained from lichens (lichen). These are communities of fungi and one or more photosynthetic partners (e.g. green algae, cyanobacteria).