It's not explicitly stated, as far as I know. The listed Free Actions in the PHB (p. 128) don't draw AoOs, but I haven't seen anywhere that says flat out that every free action is immune to AoOs. So, if you make an item that activates as a free action, you could still make it draw an AoO if you wanted to.
BUT, you shouldn't. Command-word items don't draw AoOs. Use-activated ones only draw an AoO if the use involves committing an action that provokes an AoO in itself (and quickened spells don't draw AoOs). The concept of a AoO in general is that the target drops his guard while doing the action, and a Free Action takes negligible time.