GPS time doesn't have leap seconds. GPS time contains leap seconds, but it will not recognize any further leap seconds. GPS time contains nine leap seconds-- the nine that occurred before creation of GPS time in 1980. GPS time is 19 seconds ahead of TAI (9 leap seconds plus the 10 differential between utc and tai from 1950 or 1960) and 17 seconds behind UTC.
This number (GPS-UTC) will grow as more leap seconds are inserted in the future. This is not the entire picture and it is important that people do not hard code this assumption into their programs. Leap seconds can also be removed, that is GPS-UTC can also shrink. This has never happened but there is no point in hardcoding incorrect ideas about time scales in your program.
ntpd will act like all of its sources are insane, with huge offsets and jitter values approaching -17000 milliseconds. Jitter values will not approach 17k milliseconds. Jitter is the variance between repeated measurements of a configured peer.