I see many potential use cases for this project:
1. As a developer, I have had customers paying me to contribute improvements to open source projects they depend on, this case is very tricky because there is no guarantee that the upstream project will accept the change.
2. As a company, we have had the need for some improvements to our projects that we don't have time for handling, a platform like this could have helped us.
On the other hand, I see some potential issues:
1. As a developer, it is hard to invest the time on a task when there is no guarantee for the payment, imagine I start investing 1 week in completing a bounty just to see someone else getting its PR merged before I finish mine, have you considered adding a locking mechanism? let's say, if I get the bounty assigned, I get up X time to deliver, otherwise, the bounty can go to someone else.
2. As a company, I'm not sure that many companies would be willing to commit to the 23% fee, maybe there is a way to structure this in a friendlier way? for example, taking a 20% fee up to $Y, even Upwork has a different % based on the amount paid by a company to a developer (staring at 20%, going up to 5%).
3. As a company, assuming a bounty can get locked to a dev, if I get many people interested in a bounty, how do I decide which one to pick? displaying historic data about devs could help.
In any case, good luck!
EDIT: I also haven't seen how a dispute would be handled, let's say, a dev sends a PR but a company rejected it but silently takes the code to use it. The inverse case could happen, a dev submitting low-quality work and demanding the company to pay.