vincevincevince - 7:46 am on Dec 11, 2008 (gmt 0)

I was suggesting that they wouldn't need to know that as long as they have a forum

Could really come back to bite you. For example, when the client decides to sell his site and discovers he doesn't own the forum he paid you to create - even worse that he can't sell it without having to release the full source code to anyone for free. Another example is when his forum gets hacked by a robot following the latest phpBB vulnerability - how are you going to explain to your client that he needs to keep updating the forum you built for him by using a third party package he's never heard of - and more to the point, who will pay for this updating work?

If you plan to use open source components, you really must inform your client of this and make sure he realises the implications. Give him three prices if you like; the highest for you to build it entirely as 'work for hire' so he owns everything 100%, the second for you to build it and give him a perpetual license (allowing you to reuse it for future clients as well), and the lowest for you to base it on open source software. That way you aren't hiding anything and he is able to decide how much the advantages of proprietary software are worth.