Games and Rounds board is for "contest" and Gambling-related events than recruitment.
Services is valid as long as you're asking for a "service" paid in Bitcoin (Bounties for Altcoin payments).
G & R Board is the best place to post it. It's a one-time thing and he just wants only 10 DT members to test out certain features of his gambling game.
If he posts it in altcoin bounty section, he won't get his target audience let alone the DT Members who barely visit those sections.
The real gambling audience he needs is found in the gambling board and child boards.
I have seen a couple of successful tests and review giveaways before in the G&R board like
this one