I've been licensing my FirstData (now Payeezy?) payment plugin since late 2013 and am now releasing it as open source to the community.
I had to do some restructuring and add unit tests before I was comfortable releasing it so only 4.2 is available at the moment. I plan on adding at least as far back as 3.6 but I want to see if I can get GitHub actions to work to build the release file and run tests automatically first.
The license is MIT so feel free to fork it or copy it or whatever you want to do with it. Pull Requests are appreciated but will be rejected if the feature is too specific and not applicable to most users.