[marginalia_nu]

Well it's open source and contributions are welcome, though it's a fairly sprawling java project that's probably not the easiest to get into still (through no lack of effort making it more accessible): https://github.com/MarginaliaSearch/MarginaliaSearch

If you have spare dollars but not time, you can also contribute to the war chest: https://about.marginalia-search.com/article/supporting/