Hopefully the generic should be the same as the brand name. Also, to combat the loss in revenue from generics, the maker of Colazal (Salix) has partnered up with another pharma company to manufacture a generic version itself - so I would assume their version should be closest to the brand.
It seems that there will be 3-4 companies marketing generic versions of Colazal. Salix is working towards getting FDA approval to market a once-a-day granulated mesalamine form that's not available in the USA yet (but is overseas - Salofalk Granu). It's good to see that there's some healthy competition going on.