I am on a project. And I am going to share this project on gamejolt. This project totally free. Am I need to pay something to Unreal Engine 4?
INAL. No, but keep in mind that money input like Kickstarter and Donations count towards your Income too.
Quoting the "Releasing Products " section of the FAQ:
If I release a commercial product, what royalties are due to Epic, and when?
Generally, you are obligated to pay to Epic 5% of all gross revenue after the first $3,000 per game or application per calendar quarter, regardless of what company collects the revenue. For example, if your product earns $10 from sales on the App Store, the royalty due is $0.50 (5% of $10), even though you would receive roughly $7 from Apple after they deduct their distribution fee of roughly $3 (30% of $10).
What about downloadable content, in-app purchases, microtransactions, virtual currency redemption, and subscription fees, as well as in-app advertising and affiliate program revenue?
Revenue from these sources is included in the gross revenue calculation above.