Jurisdiction may be disputed, and yes, in sales disputes it might be decided that Belgium doesn't have jurisdiction over that contract if you have no subsidiaries or other relations there. Still, even in your case the "target" country law does apply for whatever things happen on their side of the border - and it may impact you. Say, if the item is considered illegal there then it may be confiscated at customs, leaving you without the item and payment; and your local courts won't help you there.

But in Google Summer of Code case, if it's treated as 'work for hire' then the host country definitely has jurisdiction as the actual work happens there. And Google has subsidiaries worldwide (used for ad sales), so they can easily be targeted.