Yes. Having access to the source is not the same as open source. I encourage you to re-read it. They also have an FAQ clearly outlining the restrictions. https:

Yes. Having access to the source is not the same as open source. I encourage you to re-read it. They also have an FAQ clearly outlining the restrictions. https://www.unrealengine.com/en-US/faq https://www.unrealengine.com/en-US/faq "Can I copy and paste Unreal engine code into my own project or engine? If you use any Unreal Engine code in your product (even just a little), then your entire product is governed by the Unreal Engine EULA, and is subject to 5% royalties when your gross lifetime revenues from that product exceed $1 million USD."