Please read this KB article for detailed information regarding the SIMD instructions supported by the Intel IPP library, through version 6.1.
Understanding CPU Dispatching in the Intel IPP Library
Note that most AMD and Intel processors produced today support the SSE2 and SSE3 instruction sets. The SSE4a instruction set is unique to AMD processors and is not supported by the Intel IPP library. As you can see from the chart in the table above, after SSE3, the library supports the SSSE3, SSE4.1, SSE4.2, AES-NI and AVX instruction sets.
There are also several good articles in Wikipedia describing the differences between the various SIMD instructions sets available today.
Regarding licensing, please review the following KB articles:
Location of the End User License Agreement (EULA)
How do I renew my license?
Development Products Download, Registration and Licensing Help
Intel IPP Downloads, Registration and Licensing
Which Intel IPP libraries are "Redistributables"?
Intel Integrated Performance Primitives - Licensing FAQ
In essence, you pay a license, per developer, to download and use the IPP library to create an application. There are no royalties associated with distribution of your IPP application. That is, you do not pay any license fees to redistribute an application you build with the IPP library. The specific files you may redistribute with your application are described in the "redist.txt" file that is part of the development package.