Is there taboos on what some races can eat? Like, since feral cows and cow morphs exist at the same time, would it be considered bad for them to eat a hamburger once and a while?

That's a fun one. It depends entirely on where the race lives and their culture. (sort of like us)
SLOP is set in a place very much like the US and as a result, contains a similar mixture of cultures and a larger overlapping national identity. There's no real cultural bias against eating your own kind, but most of the meat eaters eat many of the same animals we do. Dog is not popular food in the Federated Union of States. Pork, Beef, Chicken, Rabbit and Capybara are are quite popular to eat.

Due to ignorance and misunderstanding, it is a bit weird to some to see a Vepr like Tony-Ray eat Pork or a Fel (deer) to eat venison but it happens :)

Each race has it's own diseses im sure, but are there any cross species travelin' bugs that the folks of slop have to look out for..

I won't mind learning about the different wars in the SLOP universe. The Thaikong War, The Tangun War, and the current war going on. How'd they start? What was the outcome?

Of course, Runs said "Don't forget to include the persecution of the Cuni"

and let's not forget the d20 system stats for all the main characters! :)

I'd love to play a GURP version of slop.

It'd be useful to identify the diferrent cultural or ethnic groups at work, and how they interact. Are all species one ethnic group? Or is it broad enough to be by genus? Is it complex enough that it doesn't necessarily follow species lines? If a ladrance boar from england meets a potbellied pig sow who was born in the Fed to parents who emigrated from Thaikong, is that thought of as an interracial marriage?

bah, it's probably just as mixed up as it is here. :]

Do diferrent races have diferrent diets? Is there tension between apex predators and those lower on the food chain, or has that not been a thing since the bronze age?

The birdy folk, do their wings work or are they purely vestigial...there for show?

Me, I like the fact the (morphs?) look like you'd expect 'real' morphs to look like. If Tony Ray showed up in in the real world, He'd look like he does in the comic, not with a stylized uncanny valley look. :>

Also, do the morphs have holdovers from their feral kin? Say for example, would a platypus bloke have the poisionous spurs...or just the spurs but no poison?