GPL is a hostage negotiation, or at best barter. I'll give you my code if you give me yours. There is nothing "free" about it in my mind.
MIT/BSD/Apache is true freedom "You can have my code, no strings attached, do what you want with it, just promise you will tell people it is open-source and who wrote it!"
#GPL #OSS #OpenSource #FOSS #Software
@drewfer LGPL is an improvement but still stifles contribution for much the same reason