I doubt that Seamonkey could adopt Goanna, politically.

Most of the Seamonkey Council are Mozilla employees who work on Gecko and Firefox too. Awkward.

I doubt they could, practically.

Goanna is just a rotting fork of some dead Gecko code. Pale Moon is slower and less standards compliant than Firefox and probably has more security problems (does anyone think one guy can really maintain all of that code?).

The license to the code says you can run off and make an incompetent broken fork. It wouldn't be Free (as in Freedom) unless other people were free to fork it and do better or worse, but I don't see a case for "better" with Pale Moon. How is slow and less compliant with standard better?

MC Straver said he changed the name to avoid the impression that Goanna was just a bitrotting Gecko engine, which anyone can see that it is by pointing it at HTML5Test, and to avoid Trademark Infringment, which Mozilla does enforce. I'm guessing he got a friendly tap on the shoulder about his rotting Gecko fork.