OpenAL is an API for audio. Rockbox audio API is completely different, and you can't simply "install" OpenAL (as well as other Linux packages) on Rockbox -- Rockbox is not a Linux port but has its own kernel. Therefore it's completely incompatible with software designed to run on any major OS. I'm not familiar with Rockbox audio API to tell how much work it would be to port OpenAL to Rockbox, but I bet it would be at least lots of work -- if it's feasible at all. As far as I can tell from the Wikipedia entry on OpenAL it is designed for 3D audio -- nothing Rockbox does. Also, I wouldn't be surprised if OpenAL used dynamic memory (haven't checked), something that Rockbox doesn't support.