Balderdash. Back in my C64 and Amiga days, I routinely downloaded non-GPLed source, even non-BSD source. In the early 80s, source could be found easily on BBSes, on textfile magazines, on Compuserve, BIX, UUNET, et al. Comp.sources existed for just that purpose.
People were giving away source way before RMS arrived on the scene, they just did it informally. Most people simply had no need to keep source closed for hobbyist freeware because they never stood a chance to make money on the n-th clone of a utility that they wrote for a learning experience.
For example, allow me to reproduce Matt Dillon's "license" for D-Net for the Amiga
DNET (c)Copyright 1988, Matthew Dillon, All Rights Reserved
*
* Connect a csh to a pseudo terminal pair... PORT_ALPHATERM
* NOTE!! PORT_IALPHATERM (a pseudo-terminal csh) is also available
* through the FTERM client program on the Amiga side, and much faster
* since the server for PORT_IALPHATERM is DNET itself (one less process
* to go through).
*
* -doesn't handle SIGWINCH
* -doesn't handle flow control ... don't cat any long files!
*/
Dillon produced, among other things, DNet, DCC (free+source C compiler for Amiga), AmiUUCP (Amiga UUCP implementation), etc.
And then there are the oodles of MUDs/MUSHes/MUFes/MOOs/Dikus/LPs/etcera that don't carry "modern" Open Source licenses, but "old school" "Copyright by Me, use as you wish"
The GPL is an insidious license, one that denies the very idea of an honor system, of altruism, of *fun of coding*. It makes the assumption that in order to contribute one needs to be "paid back" by forcing others to give their contributions back to you. It mandates reciprocity and denies the main essense of the wellspring of open source which is people having fun and engaging in learning.
GPL people make alot of noise about the dire scenario of someone taking *your code*, modifying it, and distributing it to make money without you getting anything. For me personally, if someone else uses my code, that is reward in and of itself, like knowing that an orphan got a family. I personally could care less whether someone else uses it without giving back. That's why I prefer BSD licenses.
On top of this is the fact that the GPL is largely irrelevent these days since the majority of new applications are distributed via remote interfaces like the web, not distributed as installable client binaries, and therefore, no one can be compelled to contribute any beneficial modifications they've made to GPL code which they are running on a web server.
And the "dire scenario" didn't come to pass for BSD as many people expected. Instead of commercial companies "stealing" BSD and distributing BSD modified binaries without source, the major mode of theft (in the early days of Linux) was Linux GPL hackers stealing BSD driver code to bootstrap their own drivers they were writing.
The fact is, *huge* amounts of non-GPL viral code exists, like Firefox, like Apache licenses, like BSD, and despite the "flaws" in these licenses (according to GPL zealots), more than enough people exist in these communities to continue to push these applications.