The live data-feed is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 2.0 license. This allows free non-commerical use of the live data-feed. Commercial users will need to contact the MetaBrainz Foundation to arrange for a commercial use license for the live data feed.
For commercial use, the data must be hosted by the company that wishes to use the data for their own products. This puts all reliability/availability issues into the hands of the commercial user, so that the user can ensure the proper availability of the data for their own customers. The MetaBrainz Foundation currently does not offer services to host the data for commercial customers