I'm trying to find the name of a book series (maybe a trilogy) with this story line. I feel like the title is something to do with distant star or remote sun, but I can't find it.
Humans were almost wiped out by a disease and have retreated to a planet and lost track of earth, they may even have lost the belief that there was an Earth. They meet two alien races, one of which they call crabs. At least one crab blows itself up on board a human ship. The crabs don't have names until they distinguish themselves in battle. One does that, challenges for leadership and befriends the humans.
The humans find an ancient ship that is able to make other ships. Another race made it and want it back. They usually rent it out to other races with a technology lock on it so it can't be used to create more manufacturing ships.
There's some switching back and forth about which race is better to be aligned with and whether one of these races was the architect of the plague.
There is another ancient ship in here too. The Crabs have been guarding it for the humans.