UPDATE: In related news, Microsoft of all companies just submitted several thousands of lines of code to the Linux kernel under GPLv2.
Zed has personally experienced what GPL-fans (including myself) have long seen as weaknesses of open source licenses that are not copy-lefts. GPL lays down the common understanding of open source in ways that avoid exploitation, while at the same time allowing the GPL to be used commercially.
The heart of the GPL is about protecting the open source community so it can continue to grow organically where projects build on each other to produce amazing things. The problem is when $BIG_CORP decides to take the open source code, rebrand it, sell it, and contribute nothing back. It halts the organic nature of open source at the hands of greedy suits.
I have nothing against companies profiting on open source code. If someone somewhere makes money on the few petty projects I’ve done, great. Use my code, learn from it, integrate it. But please also pass that knowledge on to others to make it better and more useful to the world at large.
We in the open source community are standing on the shoulders of giants, but lets not get bled to death by corporate giants.