Has anybody used either the SeaLect Tru Course or KajakSport-Navigator rudder?

I have built both systems into kayaks. We are currently using the KS Navigator on our family's "Atka-16" touring baidarka. Like Alec explained, they really do use the same, basic system of a plastic blade that slides in a housing. Here's an "animation" of the KS version:

They are both easy to use and retract completely onto the deck. Both operate well in conditions. Both kick-up on landing or when they hit something. Of the two I prefer the KS version. It seems more robust, uses much fewer components (maybe 8 total), and just looks more elegant. One nice feature on the SeaLect version is you can set the blade depth via a stop block.

Here's the SeaLect on a S&G project from 2014:

Here's the KS Navigator on the Atka-16:

Do either of them allow 'kick up' if kelp or harder objects are hit?

Yes. Both are held in the 90 degree down direction by the downhaul bungees and "lock" in place small indents in the carriage. When the blade hits something (like the bottom) they rotate up and kick up.

FULL DISCLOSURE: I am an authorized seller for both SeaLect and KajakSport.