Actually it would be so simple: I give you source code, you give me changes back, we're even. [...] If you make hardware that locks down software, it's your decision as a hardware maker; it has no impact on my decision as a software maker to give you the software. [...] To me the important part was always: I give you software, you can do whatever you want with it; if you make improvements, you have to give them back. (source: https://www.youtube.com/watch?v=PaKIZ7gJlRU).
I wonder if GPL3 didn't have quite so many changes if it would have been more widely accepted.
But listening to RMS he said he didn't realize that companies would "tivoize" everything so he added:
"(0) The freedom to run the program as you wish, for whatever purpose."
Personally I think it kind of sucks that much of computing coming out nowadays has locked bootloaders.
Good software, which is not used due to (unnecessary) legal uncertainties, and thus cannot benefit from the support of potent companies, is of no use to anyone, neither in the short nor the long term. The sooner legal uncertainties are removed, the better. Unfortunately, companies avoid legal disputes, often at all costs; that is why it is so easy to blackmail them with out-of-court, very often unfounded claims from patent and copyright law.
When I buy a product, I want it to work well and have good value for money. For this it is irrelevant if the bootloader is locked. If I want to make a system to tinker where I can replace the firmware, I buy a Raspi. The Raspi also benefits from contributions from companies that use Linux in devices where I might not be able to replace the system.
It is similar in most other jurisdictions too, but wording predominates in practice.
EDIT: clarifications
What if a clause is ambiguous to benefit both parties equally, but not at the same time? Are both parties forbidden to act on their own in those cases?