I recently watched this show and enjoyed the music, however the only functioning link I have found so far was for the opening single.
There was a thread on this forum with a dead link from 2007: Thread 43796
Searching hikarinoakariost didn't turn up anything, and the site skyanimes seems to have 404ed all it's OST links.

Would anyone happen to have a working download link for this OST?

I did some SERIOUS digging and found a good download for it.
https://mega.nz/#!hQYGRTxS!dH0AsAtTrkdfZu7T025hjDgxQvp50J63FBKv1-k8qdU
Took me a few days to pull this link up, so I want to share it with anyone else who may want this wonderful OST.