(I’m not a lawyer and this is not legal advice)
could be interpreted by some as committed to protect a free philosophy in their product.
That would be a misinterpretation. Copyleft and permissive licenses are both foss and both permit users the same freedoms required under FOSS definitions. 
Also, the AGPLv3 in particular, while still FOSS, can be used in a quasi-proprietary way in practice. Weaponized Open Source
But I feel that a copyleft license complements AliasVault’s other trustworthy aspects.
You have yet to explain how licensing and trust relate, or why copyleft would be considered more trustworthy. If anything, the AGPLv3 in particular is sometimes an indicator of distrust, as it has a history of being used to bait and switch.
I can’t shake off the possibility that proprietary abuse could befall the software, like with what happened with MINIX and Intel.
Permissive licensing doesn’t mean someone can just take your code and make it proprietary. Code released under a FOSS license is FOSS forever, whether it’s copyleft or not. If anything, copyleft licenses like the AGPLv3 are more susceptible to being taken proprietary, as explained in the article I linked above. It makes the project a one way street, especially if they have a CLA. This is because they can always take their own code proprietary in future versions (code owners are not bound by their own licenses as they own the copyright). Sure, we’ll still have the old AGPLv3 version of the code, but that means we’ll be forced to release our changes as AGPLv3. Meanwhile they can take previous contributions proprietary because of their CLA. This isn’t a hypothetical, it’s a strategy that’s actively utilized.