There won't be any issues. Surly hubs, DA cogs and Formula hubs have the same cog threading ( 1.37" x 24 TPI). Check it for yourself; on a site where you can buy any of these things they will usually mention the threading standard.

[Edit] apparently this is only true of cogs. Well at any rate, Surly cogs and DA cogs are both 1.37" x 24 TPI (according to internet sources), and Surly cogs definitely work on Surly hubs, so there shouldn't be any issue running DA cogs on a surly hub.