Can I use the freevec library on e500 core which supports SPE? If yes, how can I do it? In the libmoto library, I can do it.

You would have to recode all the functions to use SPE intrinsics instead of AltiVec ones.

Since it is all in C that shouldn't be a huge problem.. a lot of the functionality is identical, although some of Konstantinos' math proofs rely on a 128-bit register I think (SPE only has 64-bit if I recall).