League adjustment is the money paid to your team for existing basically. For teams below regional minors (capped leagues) you get 600 each game day and some larger amount paid on day 0.
It changes once you get past that, for example in regional pro we got:
Apr 23, 2012 $506,250.00 League Adjustment
Apr 22, 2012 $2,700,000.00 League Adjustment
Ends up being $10,800,000 by the end of the season i believe. Might be more, i don't remember offhand if we get paid for the 4 playoff games. You have to stay out of the red (positive cash) to get this money. It's probably in the wiki. Yep here you go, it's pretty out of date but gives you something to look at: http://wiki.goallineblitz.com/index.php/Media_revenue
League bonus is the money paid to your team for other teams being financially irresponsible (ie over the salary cap) which you already knew.