If their ANN thread is outside Games and Rounds, yes, it's breaking the rules. Some examples from various rule-related posts around the forum (emphasis added by me):
Games and rounds (child board of Gambling) - "Spreadsheet games, forum-based games, and discussion of individual rounds/games on other sites." All Bitcoin giveaways, raffles, contests also go here.
Most giveaway threads are no longer allowed in the Alternate cryptocurrencies sections. From now on, posting or replying to such threads could result in being banned. Existing threads will be locked.
Specifically, you are not allowed to give people any incentive to post insubstantial posts in your threads. You can't offer to pay people who post their addresses, usernames, etc. You can do giveaways off-site and link to the giveaway page in a thread, but you can't give people any bonus for replying to your thread.
Similar threads are already restricted to Games and Rounds in the non-altcoin sections, but the giveaway-related post volume is so high in the altcoin sections that I've decided to just ban them entirely here.
To be specific, I'm referring to "Post in this thread for free x". That belongs in Games and Rounds. Though it isn't limited to that, in general you shouldn't be giving people incentives to post in your thread, it's disruptive to actual discussion.