GPL v3 keeps this spirit, if you really want your server side web library cannot be used for server based closed source projects (without a fee), the AGPL v3 (Affero GPL) was invented for. This license was invented for network based applications.

Ext-JS guys should be picked AGPL to make money with commercial licenses (the GWT version is actually server based). Selecting GPL introduces a license hole.

A JavaScript library is another history.

ItsNat, Natural AJAX, dual licensed AGPLv3/commercial from START.
http://www.itsnat.org

Personally, I license all my code BSD (without the advertising clause), especially my libraries. Why? Because I’m not so full of myself to think that the code I’m writing is so very important that I must be allowed to control anyone who uses it.

I have a Java coding background, and my website is an experiment in creating a blog from scratch, while opening up the code for the site and all the libraries it uses (everything is available via Subversion). The goal is to develop some best practices so that others can benefit. The GPL would be completely unsuited for that purpose.

Without getting into all the dirty details, a GPL’d Javascript library *probably* requires all other Javascript libraries expressly required by that application to be available under GPL-compatible licenses. This would include your own Javascript code for your application, but it probably would not include any Javascript code that the browser renders outside your control (e.g., you use a GPL’d Javascript library to create an OpenSocial widget, that doesn’t mean the other widgets a user has must also be GPL’d).

It also would not extend to any server-side logic, as the separation between client and server traditionally has been held as “distant enough” to not trigger GPL terms. That’s why things got icky when MySQL put their client library under the GPL — previously, you could create a MySQL-using application without triggering GPL provisions, because the client library was not GPL’d (I think it was LGPL’d). Similarly, if you were to use a pure GPL Web browser, it doesn’t “infect” every Web site you visit with GPL terms.

IANAL, NDIPOOTV (I am not a lawyer, nor do I play one on TV). If you are serious about this, get serious legal assistance to match. But, a rough-cut approximation is: a GPL’d Javascript library would affect client-side code of yours, but not server-side code.