If I write a public-facing commercial website, and use a GPL javascript library and/or binaries without modifying them (such as plupload), would I be required to make the source for my website available? Is that considered distribution?
That component is just an example. I know a commercial license is available, but would I need a commercial license if I wasn't modifying the source code of the component?
GPLv2 does not mandate that. Actually, there is a modified version(AGPL) that is specifically designed to force web apps to release the code. If the binaries are running on the server, you don't have any obligation under vanilla GPLv2.
No, and it doesn't matter what the license says (in the United States). As a matter of law, you are not copying the covered work and you are not distributing the covered work. So you don't need a license. In the United States, the ordinary use of a work does not require any sort of license.
The GPL only applies to people who agree to it. Generally, you agree to the GPL because you want to do something that copyright law says you may not do without a license such as distributing or modifying a work. If you aren't doing anything that copyright law reserves to the copyright holder, you have no need for any license.
