If I well remember, you can partecipate if you already worked for a publisher, but only if it isn't on the top 5 most important\biggest publishers of your country. There is a list of american publishers that will get you out of the contest, and this rule for people from other countries. I don't think you''ll have any problems, especially because the contest you won will give you work in the near future, but not before the end of the Top Cow contest.