Before the GPLv2 we had the AGPL, which made it explicit that you had to divulge any server side code.
Now, with the GPLv2, it is possible to use Aloha freely in most websites/webapps. You don't distribute your website/webapp and therefore are not bound by the GPLv2 to divulge your website's source code.
The GPLv2 _would_ take effect if you distribute your website in the traditional sense - a package that someone can run himself.