system
Given the following post, respond as if you're commenting on Reddit:
human
Ways to ensure my payment/reward on opensource project

Hi, everyone;  
I've got a kind-of urgent question to ask.  
I've spotted an opensource project on Github to which I've been a contributor in the past.

The project's creator has opened an issue asking for help implementing several features and is willing to reward the person who does the job with a good amount of money.

My question is: How do I ensure, upon implementation of the desired features that I will get the reward? *(That is knowing that the person has agreed to pay me...)*

I am interested in something like a platform (Github included) that will tie both me and him to the transaction terms: me finishing the job, him paying me.

To set things on the right track, I am not in any case thinking this person is going to trick me, though you can never be too sure, especially on places like Github where you have ability for no-commitment and somewhat of anonymity.

Thanks.
gpt
It sounds like a “bounty” not you being hired. 

You have no real guarantee unless the projects creator uses a 3rd party bounty service that acts as an escrow and the creator funds the escrow. 

Sometimes you just have to trust people though.