The web page states that the Chameleon can check the King from an adjacent
square and this is correct per Abbott's rules for Ultima in 'Abbott's
New Card Games'. He states that a Chameleon may capture a piece if it
mimics it's move in direction and distance. So a pawn can only be
captured by a Rook move and a King can only be checked from an adjacent
square.
Leaping a Long Leaper does not invalidate the mimic of another piece. This
seems illogical at first glance but really is logical. The idea is that
making a capture of one piece does not prevent the capture of others. If
the Chameleon had made a Rook move away from a Withdrawer that sandwiched
a Pawn, both captures would be allowed. Abbott believed that leaping a
Long Leaper should not preclude other captures.