I have the retail version of The Void, unfortunately I don't have a DVD drive anymore and so a friend copied the DVD to a USB stick.

Unfortunately, the game has one of those diabolical copy protections built in and prompts to insert the DVD at startup.

Unfortunately there is no information or updates on your website.
Is there any way to get a patch or a key for the GOG version (No Steam Key Please)?

Thank you Dyll

Yes, rebuying the game here... Not the answer you wanted, I guess but cheaper than buying an external USB DVD player.

You should ask the developers or the publishers. The german retail edition contains SecuROM as DRM, therefore it won't run on the latest versions of Windows even with a DVD drive. Please, read here for more information on the subject.

Why should I buy the game twice, I won't do that.

Last night we created a 120 MB Diabolic ISO image of the DVD, which I now load via Diabolic Tools into a Diabolic Drive.
This works great, so much for the diabolical copy protection. I also found a diabolic patch, but there you do not know what you get in the "house". Let's see what a comparison in the Diabolic editor is to see, maybe only a few bytes are changed. Thanks for the link.

That is the smart solution but I did not want to write that in case it breaks this shop's rules.

You are right. That is why I have revised my choice of words.

EDIT:
But this much I learned from the whole thing, SecureRom and SafeDisc are disabled in Windows 7/8.1 and removed altogether from Windows 10 on because it had security holes.
The patch is available for the GOG ... Versions.
So there would be nothing against removing this security hole and providing a patch for the retail version.