wow

May want to add Totem Warrior (Barb) to 'Available for'.

Same applies to Beast Sense.

so thats how all those random disney characters do it...

Does use of this burn a spell slot or is this more of a passive thing my Oath of Ancients Paladin can just do? 

It uses a spell slot, unless your character can cast it as a ritual (which makes it take 10 minutes longer to cast but keeps you from having to use your spell slot)

Thanks! I'm still learning this stuff after one campaign finished. 

wow

I like the idea of a Beast Master who has been mad at their Animal Companion and a warlock (has an invocation which is this for free) acts as a therapist for them. Bonus points if it’s the warlock and animal in one room and then the ranger and the warlock’s familiar somewhere else, using Voice of the Chain Master.

could i understand a kenku child with this?

I would say no. First of all, Kenkus are humanoids, not animals. But, they would not be unable to communicate at all, they could speak phrases they have heard in common to you.

 [...] Finally, to ensure that the kenku could never divulge any secrets, their master took away their voices. [...] Although unable to speak in their own voices, kenku can perfectly mimic any sound they hear, from a half­ling’s voice to the noise of rocks clattering down a hillside. However, kenku cannot create new sounds and can communicate only by using sounds they have heard. Most kenku use a combination of overheard phrases and sound effects to convey their ideas and thoughts.

If it's cast as a ritual, I don't think it burns up a slot. If its parry of a racial feature I don't think it does either. I rule a class feature spell like this would be a ritual.

You don't have to rule it's a ritual, because it has the ritual tag.

And casting as a ritual never uses a spell slot. That's the bonus for it taking so long to cast. You're drawing on the weave, and using that to power the spell, instead of your inner reserves. 

"To cast a spell as a ritual, a spellcaster must have a feature that grants the ability to do so. The cleric and the druid, for example, have such a feature. The caster must also have the spell prepared or on his or her list of spells known, unless the character's ritual feature specifies otherwise, as the wizard's does." - PHB

With this in mind, the Totem Barbarian can ONLY cast this spell as a ritual. 
Paladins do NOT have the ritual spellcasting feature. This spell is added to the Oath of the Ancients Paladin spell list, but they must use a spell slot when casting this spell. 

can a bard who casts this be able to understand a druid in wildshape?

Although it can be ritual cast, I cannot imagine whatever wild animal you are attempting to communicate with; would hang around for the ten minutes necessary to start talking.

I agree about the animal hanging around, but you could cast Animal friendship (lasts 24hours), then ritual cast being able to communicate with it, then ask it for information or favors. Much better then just one of the spells but not needing to lose two spell slots.

The ritual is useful if the specific animal you want to talk to is your pet, or a druid in wildshape, because they would probably have patience. Or maybe you don't care which animal you are communicating with, and any animal would do. For example, if you want info about whether people ever pass through an area of the woods, or if you're lost and need to find the way to the nearest village.

For an interesting example. (non D&D) of what a warlock-style character can do with this ability, read _Old_Nathan_ by David Drake (I think that's the author).  Bonus, it is available as a free Kindle ebook, so it doesn't cost anything if you already have a Kindle (or the free app).

can i use this spell to speak with someone else Familiar?

No, because a familiar is not a beast. Per the description of Find Familiar, the caster decides if it’s a celestial, fiend, or fey that just assumes the form of an animal.