Our Labs version is released under the GPL license. That means that you are free to use and modify the code. However, if redistributing (which it sounds like you might be if giving it to a customer), you need to also make all the code / improvements you write available as open source, also under the GPL license. This way, the whole community can benefit from your improvements. If this is not an option for you, as it is not for other users, then we sell Alfresco subscriptions under another license, which allows you to modify and redistribute without having to contribute back your code.
Also, "latest stable code from SVN" - the Labs version has no guarantees that it will be stable - it is code that is being actively developed. If you want stability and more predictability, you should contact our sales for the Enterprise version of the product. We harden that version more and put it through a long and rigorous QA process, certifying on multiple stacks of DB / App Server / OS. If you care about your customer, this might be a wise choice. Open Source gives you the freedom to choose which one you'd rather want for your customer.
