Very interesting tidbit on the PowerEdge mailing list today... Dell seems to have built their DRAC remote server management interface around BusyBox Linux. It's a minimal, low profile Linux platform, often used in embedded situations or for system rescues, maintenance, upgrades and so on.
BusyBox is GPL, so accordingly DRAC must be GPL and therefore the source code must be available somewhere. Well, it is! Just file a service request and mention "SKU 420-3178". And this makes for low level custom builds for your specific organization, additional drivers, etc.
Update: The SKU number for the DRAC source code is also mentioned in the Dell PowerEdge Diagnostics readme.txt file.
Update2: Someone has thoroughly investigated the SKU with Dell Australia and the ruling is that the SKU does not exist (anymore). It can't be found.
Update3: Dell releases DRAC5 source code on website.