In the article, you pointed to a GNU tract on free software. In it, we find:

You should also have the freedom to make modifications and use them privately in your own work or play, without even mentioning that they exist.

In support of this freedom, the GPL puts no requirement on you to redistribute your modifications. In Section 2, your are told you may ``modify your copy [...], and copy and distribute....'' under conditions a), b), and c). a) and c) make no mention of you redistributing the program.

The rub comes in condition b), wherein you are required to

cause any work [...] that [...] is derived from the Program [...], to be licensed as a whole [...] under the terms of this License.

Condition b) only applies to you if you ``distribute or publish'' the (possibly modified) work. It in no way requires you to distribute or publish.

Thus, we see that the GPL indeed gives you the freedom quoted above, to modify the program and use it personally without passing on the changes. The GPL has no interest in prying into the contents of your hard disk, it just says if you pass this on with changes, then the changes must be distributed with the same freedoms as the original. Hence akihabara's entirely-valid remonstration. The GPL allows you to use the software without returning the favor, so long as you're only using, and not distributing, it.