Brightcove, the television-on-web company that is also one of the Business 2.0 Next Net 25 start-ups, is going to open its service to all comers later this week. Jeremy Allaire, founder and chief executive of Brightcove, made this announcement in his keynote speech at the NAB show. For past six months, Bright Cove has been an invitation-only commercial preview. The service will be available for free. More details are likely to emerge on Wednesday.