The new mechanics introduced for ship warfare, for crew quality, and fleet actions is a completely unique system not seen before in 5th edition. As a result it could work in other systems easily. Pathfinder 1, earlier versions of DnD and so on. The ships orders are not based (for the most part) on 5th edition skills, but on a contested roll or on a d20+crew quality value versus a difficult number, these could be adapted to other systems easily as a percentage value for example.
However, in the main, it was written using the OGL 5th Edition rules.