Id to release Doom3 source code

Actually, they explicitly say 'no perpetual motion machines' or the equivalent (I think they say 'You must provide a working example of something you claim is a perpetual motion machine', which comes to the same thing.) It's a special little carve-out they have to fix that specific problem.

  People buy hardware, software, services all the time.

Fact is, an idea is an abstract concept, not a physical good or a services. One cannot own an abstract concept - the very notion of that is completely nonsensical. If somebody has a an idea, and tells (gives) that idea to somebody else, both people will have that idea now. You cannot say the same of a physical good or a service.

Besides, arguing for the status quo by citing the status quo is a circular argument.

  the idea to just throw it all in the trash bin is a bit black and white.

There is but this only option, and that's to completely scrap it and never try it again. I'm honestly tired of seeing 'but that's black and white thinking' in defense of a completely indefensible position. Sometimes there are things which are simply bad - patents are one of those things.

  You could for example have (international?) patent courts that 
  would prevent monopoly-by-patent things.

You cannot fix this system - it's broken by default.

However, to "promote the progress of science and the useful arts," as the Constitution states, it's necessary to demonstrate both that patents serve as a widespread source of inspiration and teaching (which they don't do very often, as demonstrated by the relative rarity of willful-infringement awards), and that trade secrets actually do keep advances from becoming more widely available. This is hard to show, at best.

Nobody refrains from producing a touchscreen phone with a swipe-to-unlock feature because they can't figure out how... they refrain because Apple is allowed to financially destroy anyone who tries. Most patents work the same way, in that they keep people from being able to use techniques that might have been obscure and irrelevant at one time but are now obvious, no thanks to the patent itself.

Unix was originally a non-commercial product, albeit produced by paid researchers at Bell Labs (owned by a commercial entity, AT&T). And actually, Wikipedia claims that {Thompson, Ritchie, et al} received no financial support for the first version, which was developed on a spare PDP-7, so I'm not even clear if they were using paid time to work on it. It was non-commercial because AT&T had been forbidden by a 1956 consent decree to be commercially active in the fledgling computer space. It was only in 1983 (with the breakup of AT&T and the consequent expiry of the consent decree) that commercialization of Unix started, over 15 years after its creation.

So the successes of Unix pre-1983 should be lumped with the successes of GNU (founded that same year) and Linux, as being non-commercial and not-for-profit.