i want to have a discussion forum for my website and i like daniweb script .
is it develope for just using in daniweb or its available to purchase like vbulletin ?
any advice for another good script ?
What's wrong with a well-known product like vBulletin (or inVision's IP.Board)? The fact that they are well-known means visitors don't have to re-learn features and capabilities. I'd recommend using vBulletin for a new forum. That way you can focus on building up your website, and traffic, instead of also having to program a forum with a new--and possibly flaky--software. It would be just another unknown to deal with at a time you cannot afford to spend time on it.
if you want a custom made platform, nobody's stopping you from creating/purchasing one yourself, but if it's for a simple 'discussion forum', I don't see any advantage that 'll give you over using vBulletin or similar.