What would be the practicality of a widespread open-source approach in an economy? I'm not sure how to tag this so feel free to add any tags you see as relevant.

The question here is about anything that uses a proprietary approach today and applying open-sourcing to it.

What if someone open-sourced their work in such a way that it can be used by absolutely anyone on condition they put a bit of money in to keep a project going?

This instead of intellectual property or copyright sometimes heavily restricting usage and where there is not necessarily a benefit to the community.

Hope you get the gist and please comment below for me to clarify if necessary.
So suppose there is new technology $A$ that only 1 person has access to. If there are multiple firms with production technology $y=k^\alpha$ then obviously if that new technology was available to them at low/no cost, the overall productivity of society would increase (each firm has $y=Ak^\alpha$)

The problem is that it is likely the case that $A$ requires expenditure to make. You need some way to incentivize the production of that technology (at least in a basic neoclassical framework). So if you make it proprietary then the other firms may have to pay for it, or you can give it copyright so that only 1 firm has access to it. 

In Romer's endogenous growth model, firms have an R&amp;D cost to produce their final good, but they have monopolistic power in the intermediate step to ensure that they can make a profit. If they didn't have this patent then they would not produce the technology. 

There are newer/more advanced models in law &amp; economics that discuss different kinds of IP arrangements. A great question is how are things like WIkipedia so prevalent where most of the authors see no profit for their effort but they do it anyway. Ostensibly they achieve some sort of utility for it. But then they are producing a 'public good' and in that case others will freeride (so its only sustained if their utility from it is really high).