Complete and utter horseshit. What you're talking about in the last sentence is the Affero GPL.

The GPL states and has always stated: If you modify code that is licensed as GPL and want to share it, the modified version needs to be GPL as well ("share alike").

But: Nobody forces you to release anything. If you don't release software, you don't need to make a license for it. If you want, you can license it as "Adam Zochowski Super License 5000". Frame it and put it on your wall, nobody gives a damn.

The GPL only governs and can only govern what happens when you actually do release (GPLv3 uses the term "convey") software to other people.

Sidenote: This post again confirms Stallmans rule of thumb that anybody using the utterly corrupt term "Intellectual Property" is either a moron or trying to mislead you.