It is not statically linked but loaded dynamically at runtime (see my comment above). And I think the .so is not bundled by UPX/shipped with the binary either. I believe this usecase is explicitly allowed by the GPL, but IANAL, so happy to be corrected.
EDIT: Looks like I stand corrected and this is NOT the case even if you are just dynamically linking a GPLed .so; check parent's links/ask a proper lawyer/please don't sue me ;)