Can someone explain the basic requirements of Open Source Qt LGPL to a beginner?

[TGould]

I’m a automotive electronic and electrical engineer with little to no software experience.

I need to hire a developer to develop Windows GUI application that is used to configure and program a hardware device that I have designed. I’ve found someone who is extremely experienced in all of the fields that this device is to be used for and he wants to develop this app in Qt. All copyright etc will be mine.

He uses the open source version of Qt and I do not have the budget for the commercial license.

I want the app to be closed source and as hard as reasonably possible to reverse engineer.

Does using the open source version make this impossible?

Can someone explain in ‘layman’s terms’ to an inexperienced person how you can stick to the terms of LGPL without giving away your source code of making it easy to reverse engineer?

Or maybe I've misunderstood completely and I don't need to give away my source code if I use open source Qt?

[VRonin]

@TGould said in Can someone explain the basic requirements of Open Source Qt LGPL to a beginner?:

maybe I've misunderstood completely and I don't need to give away my source code if I use open source Qt?

Indeed. You are forced to make available only changes you make to Qt itself, not any app that just uses Qt

The section named "How to Comply with LGPLv3" in this blog is quite decent: https://www.embeddeduse.com/2016/04/10/using-qt-5-6-and-later-under-lgpl/