umoci currently operates under a BDFL (Benevolent Dictator for Life) model. All final decisions are made by the project owner (who is currently Aleksa Sarai).
When more maintainers join the project, the governance model will likely change to some kind of consensus model -- but until such a change to the governance model is made (and accepted by the BDFL), the BDFL will remain unchanged.
As an openSUSE project, there is an "escape hatch" governance in the form of the openSUSE Board. In incredibly rare (and extreme) cases where a decision about this project is asked of the openSUSE Board, they can override decisions made by the BDFL (with the understanding that the openSUSE Board's main goal is to reduce friction between parties, not to act as a general appellate court). This "escape hatch" is invalidated if umoci ceases to be an openSUSE project.