In conclusion: end-user pays $5 for official SLI. Now $0 for unofficial SLI.
For so long, AMD enthusiasts have to resort to unofficial patches to make SLI work on their boards but not anymore. NVIDIA has finally agreed to make their SLI technology available for AMD 9-series chipsets boards supporting the Zambezi processors based on Bulldozer architecture. Only 990FX and 990X will be supported though so no luck for 7 and 8 series boards owners. AMD 990FX is able to support 2 PCIe x16 slots or 4 PCIe x8 slots so it can run 2-way (2 x16) or 3-way (3 x8) while AMD 990X is able to support only 2-way SLI (2 x8). There is no indication whether AMD 970 can support SLI at this point of time. The AMD 9-series launch is expected to be sometime in May so look out for it.