Blades is a concept SME Server (mitel e-smith) uses to allow easy additions of upgrades or software to the server. It is very much like Windows Update. I found this note on SME Server 5.6 release notes:
Blades
* The Blades web panel has been removed from the server manager as we have chosen to focus all blades-related development on our commercially supported products. Updates to this developer release will continue to be made available as downloadable RPMs as they were prior to the introduction of the blades interface. Commercial customers will continue to be able to download both updates and additional applications as software blades..
