For programming and/or technical savvy researchers:

Here is our scenario?
We have developed an ?Add-on? module for an existing commercial
software.   We want to be able to secure our module from end users
(customers) and other outsourced programmers that we might give the
source code to.  We?d like to protect ourselves by making sure no one
can use the software for free.

One of the questions is: 
Our module is released as an .exe or a .dll file.  Is there ANY way
that an end user can see the contents of that file?  For example, if
that file calls another file, can an end user ever ?hack? (or reverse
engineer) the .exe file in any way to see what file that .exe calls?

The other question is:
What are some logical ways for us to secure our code via software
implementation?  We don?t want to use hardware, such as USB tokens.  
We thought about adding a field into our .INI (initialization file)
that contained some kind of random generated security code.  This will
work by protected us from end users (our customers) that want to use
the software for free.  However, it doesn?t seem like it would help us
protect ourselves from other programmers we give the source code to.

Currently, when the software is run, our module gets loaded and reads
configuration values from a plain text .INI file.  We could possibly
add another module that the original module calls, and have the new
module do the security implementation.   But we are stuck as to how
the new module will implement the security.  The outsourced
programmers have full access to the add-on module?s source code.

The answer we are looking for will tell us how to secure our module
given the above scenario.   We are not looking for someone to program
code for us.  Please ask for clarification before you answer the
question, in case any part is unclear.