I don't believe that there is any built-in triggering functionality in the 1483, and rather any triggering that goes on must be programmed in your LabVIEW VI. I suspect that this is what they mean by "programmable polarity." Since you just read/write to the four TTL lines directly, you can adapt your VI to interpret high or low on those lines as "active" however you see fit.
The FVAL, LVAL, and DVAL active high settings correspond to frame/line/data valid signals, which are part of the camera link interface. The settings on those can be set using an FPGA I/O node in your VI and should match the settings of your camera.