Forgive my ignorance.  :)

I am new to .Net development and I am a little confused as to how assemblies
are protected from someone stealing them.

I am used to using Delphi to develop Win32 applications and in that arena,
nearly everything (controls, components, etc.) are compiled right into the
executable.  And since third-party controls and libraries were compiled into
the executable, it was impossible for someone to steal these expensive
controls.

What protects someone from stealing third-party assemblies?  Let's say I
purchase a library and place them in the windows program's bin directory.
Can't someone else using the machine simply copy this assembly for their own
use?

Any help is appreciated, and a link to any information on this subject will
be very helpful.