First of all, let me clarify that I am in fact a developer of open source software, and we all like and support open source.
Basically, “open source” means that you can view the source code of a program. However, usually it also implies the code to be licensed under a “free software” license (free as in “free bird”, not “free beer”) like the GPL or BSD license, so that the source code can be freely redistributed, modified and used. Typically, in such a case the program does only make use of other open source or at least free components.
CDBurnerXP is free (as in “free beer”), but not open source software (OSS). First of all, this is the case because our code contains license codes for our third party libraries, which may not be published. However, even if we made all code open which does not contain confidential information, it wouldn't be useful to license the code under a free software license, because without all the external components the code wouldn't be very useful. Unfortunately, none of the components we use is open source nor free of charge, and there are also no free components with equivalent functionality and quality available.
Yeah, there are tools to view the source code of .NET applications. But since our code is *not* licensed under a free software license, you may not use the code. There is no way to securely obfuscate the code, so for the most part we don't do it.
While CDBurnerXP will never be an open source application, we consider releasing parts of the code to the public, under a free software license occasionally.