thats true ... sweat doesnt really indicate the amount of calories you burned.
you could be sitting outside on a hot day and sweat like a pig and not burn as much calories as you would if you went for a walk on a cold, winter day.
the reason why your not burning as much calories now is ...
when you do something physicaly demanding for awhile, your body becomes used to the movements that you perform. In your case, just running..shooting...dribbling ect. Your body has simply adaptded to playing basketball so your not as likely to need to put in as much effort now. Sweating can indicate the amount of effort you put into something ... but its not really linked to calorie expendeture.
Another thing to add, is that you could have weighed more back when you first started ... if you lost some pounds, and are lighter now ... you can perform physical activity with less effort. Its almost like a plateau effect, you kept playing basketball and your body adapted to the level of fitness required to play.
hope that helps somewhat.
