"Why doesn't Farcaster have $0 sign ups"

Why doesn't Etheruem have $0 gas fees?

would y'all consider reimbursing a project for the sign up fees if: 
- project proved they're onboarding quality users 
- the sign up fee was biggest barrier in onboarding the said users

been a big topic recently

The network is permissionless. Has been since last year. Nothing stopping someone.

do you want to grow the network exclusively on your terms or do you want to allow other people to grow the network how they want to too?

Sure, we'd consider it. 

But I think the bigger barrier is building all the sign up infra.

And then the definition of quality users is going to be pretty subjective.