This Linux 9P server is a 9P-to-Linux-VFS translator. No such software component exists in Plan9.
You can think of the Plan9 kernel as a 9P multiplexer. 9P in, 9P out. The closest matching thing would be e.g. a 9P-to-ext4-in-a-file translator -- but it's always "9P server talking to $FOO" (or "9P server that makes files up on the fly").
Most of the complexity of this Linux 9P server would be in translating between the unrelated worlds of 9P and Linux VFS. A more apt comparison is the size of this 9P server vs an in-kernel NFS server -- they both translate something unrelated to Linux VFS.
You can think of the Plan9 kernel as a 9P multiplexer. 9P in, 9P out. The closest matching thing would be e.g. a 9P-to-ext4-in-a-file translator -- but it's always "9P server talking to $FOO" (or "9P server that makes files up on the fly").
Most of the complexity of this Linux 9P server would be in translating between the unrelated worlds of 9P and Linux VFS. A more apt comparison is the size of this 9P server vs an in-kernel NFS server -- they both translate something unrelated to Linux VFS.