Is it possible to statically link into game build?

I'm pretty sure the answer to this is 'yes, if you have the source code' but I thought I would check anyway.

Basically I have a dll that I can sell to developers (Unity devs and otherwise). I believe I can do this fairly securely as my customer base will be fairly small. I plan on making customised dlls that only work on one machine for each dev.

If my customers want to make a game using my dll I also need security to stop gamers cutting the dll out of a game folder and getting a free copy of my dll. C/C++ devs aren't a problem here as they can statically link the dll into their release .exe, but I don't have this option with Unity devs.

Now I noticed two things:

1) Unity uses middleware (e.g. beast) that must get merged into the build exe. 2) You can statically link dlls into Xbox games.

Is there any conceivable way I can do the same for a desktop build?

Many thanks.