The edition is tied to the key, however some variations of the installation media have the key embedded and can't be changed. The developer editions I get from MSDN are like that, using that media I can only install developer edition as there's no opportunity to use an alternate key.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability