While I agree that it makes it appear commercial, I dont know that "competition team" written on the side makes it commercial. From reading apparently 31 states have adopted the federal dot standard. The highlighted portion of my first post lists an exclusion for things such as horse shows/cars/etc .. even when prizes and scholarships are given. It's a very thin grey line on if bbq comps (and I believe they would be in the same category) meet this criteria for an exception. Most of the posts I've seen where people have had a problem has been NE, specifically PA. And those people by there own word were clearly breaking the law with huge rigs (over weight) and littered with signage.
I did however see a video of a guy coming to a comp in TN getting stopped for passing a weigh station. He is the yellow bbq ministry guy. The problem I see here is, he appeared as if he could be under the 10,001lb law, and TN is one of those 31 states that adopted the federal dot code. HOWEVER he had a ton of signage on his truck and trailer also. He was let off without any problems because he stated he was a ministry.
I havent emailed the dot yet seeking clarification on the exemption. Just havent had time. I'll post their reply when I do and get it though.