How do royalties work with Patreon?

Hello, I was wondering how the royalty fees would work in the following situation -

Games created with the Unreal Engine are released for free, but the development is funded through Patreon. Games would be free to anyone (including none Patreon supporters) but some reward tiers may provide early access to development builds/alphas/betas of upcoming free games.

If you get a true donation, it’s royalty free. But if the funds give the funder in-game access or benefit, those funds are royalty-bearing.