software licensing
How &quot;infectious&quot; is Unreal Engine 4 license? What is the scope of &quot;product&quot; definition?
<p>According to Epic's <a href="https://www.unrealengine.com/en-US/eula/publishing" rel="nofollow noreferrer">EULA for Publishers</a>, they want 5% of any gross revenue you might make out of using software built with their engine, including in-app purchases and advertising, before tax deduction.</p>

<p>However, if the actual game (built with Unreal Engine) is free-to-play, does not contain anything related to in-app purchases, but all game-altering purchases are instead done on game's website, so they are not technically "in-app" anymore.</p>

<p>Would be any revenue obtained this way still subject to 5% fee from Epic?</p>

<p>It seems relatively clear that you owe them 5%...</p>

<blockquote>
  <ol start="5">
  <li>Royalty</li>
  </ol>
  
  <p>You agree to pay Epic a royalty equal to 5% of all worldwide gross revenue actually attributable to each Product, regardless of whether that revenue is received by you or any other person or legal entity, as follows:</p>
  
  <p>a. Gross revenue resulting from any and all sales of a Product to end users through any and all media, including but not limited to digital and retail;<br/>
  b. Gross revenue resulting from any and all in-app purchases, downloadable content, microtransactions, subscriptions, sale, transfer, or exchange of content created by end users for use with a Product, or redemption of virtual currency, either within a Product <strong>or made externally but which directly affect the operation of the Product</strong>;</p>
</blockquote>

<p>The first line of the agreement seems egregious though, lets say you make a moddable game that you release for free. Somebody makes a mod and charges $100 for the mod and they get the revenue. It seems like this is saying that you, the developer, owe $5 for each sale of that mod. I don't see that as enforceable. </p>
