First, on the MattMo trade:
"This was a pure salary dump - the Bucs are paying the entire contract. Why, Dave? Why? Props to Sabean, but on June 1st he might've gotten a good prospect plus the same salary relief."
LOL @ the first part, and re. the second, it looks like the Gigantes may have gotten two decent prospects and extra salary relief, though.
Second, a plain n' simple explanation of the waiver trade rules are posted here.