Oh ya, you'd have to use that in fall or spring. This is another product from their site:
Organic Liquid Lawn Fertilizer
That might be better.
If you can't find anything else...use the non-organic fertilizer to kill all the weeds, throw down some soil on top after they've died and seed it (make that OVER seed it) right away and then water the hell out of it. Try and choke out any new weeds. Then use that corn gluten in the fall and spring. Although if you have grass all year round then that is useless to use I guess. I would just keep seeding and weed anything that comes up after by hand. Scotts and some other companies also make some organic fertilizer that work pretty good. I use mostly Scotts on my yard.