RadeonHD supported R500 and up (where the display engine got _completely_ changed), and our plan was to have Radeon support R100 through rs480 (and do it well and finally stabilize). There was a very clear division there, one that made perfect technical and practical sense.
RadeonHD made sure that HW documentation went out. We never did accept documentation from ATI (and it was ATI which was forced to provide this documentation, AMD had no access itself - and this is why we only got limited documentation), which we were not assured would go out. Mr Bridgman from ATI has broken that promise on several docs that i still have in my possession. The free docs dried up the second RadeonHD died, ATI never wanted to produce these, and you all just got docs _because_ of radeonHD. If anyone had exclusive access to documentation, then it was the Radeon project. We repeatedly caught ATIs Mr Bridgman providing information and documentation to the other project first, before talking to AMDs partner.
And finally, RadeonHD was a SuSE project, with half the developer time paid by AMD and the other half provided by SuSE, to ensure that there would be a technical solution which suits both parties. Novell was happy to take some of the marketing noise (and the money, to strangely redistribute it over the company), but that was about it.