Starting with the 7th version, Red Gate has decided to charge $35 for .NET Reflector. Company has announced that this policy change was due to commercial reasons.
.NET Reflector is one of the best "essential" tools used in debugging .NET Framework related issues. It uses reflection classes and converts IL code into .NET code (it can be called some kind of "reverse engineering").
For more details, please see Red Gate's web site:
An open letter to the .NET community
Thanks for the comments. Prior versions won't be free after May and it will be forced to update to v7 which is not free at all!