When they call three streets and then open pot the river?

[registrar]

Ladbrokes $5+a Villain is bad. First hand, he open limped a2o from utg+1 and then voluntarily showed when the hand was checked down to the river. I haven't played on Ladbrokes for a while but I always found the default style very tight (no antes, see). There is a bet pot option.

Prima Poker skin
No Limit Holdem Ring game
Blinds: $10/$20
10 players
Converter

Stack sizes:
UTG: $1705.00
UTG+1: $2000.00
UTG+2: $1960.00
MP1: $2040.00
MP2: $1960.00
MP3: $2090.00
Hero: $1970.00
Button: $1970.00
SB: $2315.00
BB: $1960.00

Pre-flop: (10 players) Hero is CO with J[img]/images/graemlins/spade.gif[/img] K[img]/images/graemlins/club.gif[/img]
6 folds, <font color="#cc0000">Hero raises to $60</font>, 2 folds, BB calls $60 <font color="aaaaaa">(pot was $90)</font>.

Flop: 9[img]/images/graemlins/heart.gif[/img] K[img]/images/graemlins/diamond.gif[/img] J[img]/images/graemlins/diamond.gif[/img] ($130, 2 players)
BB checks, <font color="#cc0000">Hero bets $90</font>, BB calls $90 <font color="aaaaaa">(pot was $220)</font>.

Turn: 8[img]/images/graemlins/spade.gif[/img] ($310, 2 players)
BB checks, <font color="#cc0000">Hero bets $155</font>, BB calls $155 <font color="aaaaaa">(pot was $465)</font>.

River: 9[img]/images/graemlins/club.gif[/img] ($620, 2 players)
<font color="#cc0000">BB bets $620</font>, Hero tries to remember what this means.