[vitriol83]

The objection is you're committing fraud. You're soliciting 'donations' for a third party (everyone committing to a project) without their consent. Unbeknownst to the donaters you're then keeping these 'donations' because the third-party has no interest in taking them. This is pretty shaky ground to be on, and it only takes one person to decide to take legal action against you.

[pbreit]

They should simply state and then execute that refused donations will be sent to other projects or returned. I don't think this is that big of a problem.

[benologist]

They don't do that, they just lie.

https://tip4commit.com/github/django/django

    Project maintainers have decided not to notify new 
    contributors about tips and they probably don't like
    this way of funding.

Then they return the tip to the 'project' pool which is themselves for unclaimed or unwanted funds:

    Funds that are not claimed during 30 days get returned 
    back to the donation pool of the project

The donor is deliberately deceived about whether the person or project will ever get the money.