(Original author and former maintainer of Gumbo here.)

Yes, it does need a new maintainer, or maintained fork. I finally lost my commit rights to the /google GitHub org about a year ago, 2 years after leaving Google. So I don't actually have the ability to merge pull requests anymore. I still have some friends at Google, some of whom were involved in Gumbo's development, but they've moved on to other projects as well and likely wouldn't be able to take over. I'm working on a new startup idea myself, so my time is fairly limited, though I can answer questions if they come up.