Don't forget that web services are a great way around the gpl. Just slap a subscription fee on there and don't distribute the server-side code and you can do whatever you want with it and/or charge whatever you want for it without being in violation or giving a competitor a chance to copy you. worked for Google.
gpl client-side code of course you cannot protect in this way (except your trademarks).
this is an important distinction. Everything on the web is copyrighted and you can't just go and grab images/html/css/javascript without permission from the copyright holder.
And view source isn't going to show you much when looking at sites like Gmail where the code is generated by a compiler that makes it as obtuse and unreadable as machinely possible.
GPL requires that users have access to the preferred form for modifying the work. If you're using coffeescript or a state machine graph or whatever, the generated javascript is more like object code than maintainable source.
There was a draft of GPLv3 that included such a clause. This was dropped with the development of Affero GPL license. The final version of GPLv3 dropped all language regarding web services. If you want to use a GPL-like license for a web application, then the AGPL is the license to use.