ThreeSixtyGiving welcomes contributions to its software projects.
If you are able to work with GitHub then please "Create an issue"
Before creating a new issue check to see if the issue already exists. If not, then please do report it. If you have permissions to assign the issue to people and milestones then try to select suitable options.
Authors should have the copyrights to any contributions and agree that the contribution is to be licensed under the same license as the project.