Subcontractors should always spell out that some parts of the delivered project will use MIT licenced code, or code licenced to the subcontracting company itself.<p>Personally, when I do business development and two companies end up co-authoring a library (like say a new plugin), we always specify what parts of the new library are for the company we helped write the plugin, and what parts are &quot;ours&quot;.<p>Sometimes we&#x27;ll write a bit and say &quot;this is yours, we&#x27;ll never use it again&quot;, and sometimes we&#x27;ll say &quot;we wrote this, you can use it, but we&#x27;re free to give it to anyone else too&quot;.