THunderbird is buying or acquiring K-9? Isn't K-9 FOSS? The OP says only, K-9 Mail officially joins the Thunderbird family (unless I overlooked something).
> And cketti [lead dev] has already joined the full-time Thunderbird staff, bringing along his valuable expertise and experience with mobile platforms. [...] To accomplish that, we’ll devote finances and development time to continually improving K-9 Mail.
Acqui-hires generally discard the acquired organization's product; where does it say Thunderbird is doing that? It looks like they are embracing it.
There's no indication of IP transfer so it seems like this is not technically an acqui-hire, but not for the reason you're stating.
I personally see this as a way for cketti to get acqui-hired and maybe get away from K-9 Mail. The amount of hate directed towards him from the userbase (mostly justified, sorry to say) has been substantial and I can't imagine he really wants to continue dealing with that.
Hopefully Thunderbird will do another UI redesign and fix the mess that was made. I ditched K-9 after the new design came out two years ago.
Given that KMail is really the only true open-source non-janky Android email client it's incredible to me that people can be so uncharitable.
With the UX changes came long-desired fixes. KMail may be the only O/S mail client at this point with a fully working IMAP search (after Apple Mail screwed it up years ago). Plus they fixed a super-irritating power mgmt issue.
Thunderbird isn't acquiring K-9 to kill it or merge with an additional product, they're buying it so they can increase its development speed and then put their name on it. That seems to me like about the best acquisition goal that they could have -- basically saying, "what exists is good, instead of building our own thing let's just pour resources into what exists."
It doesn't seem that conceptually different from what companies do with products like Blender, where sponsoring more development on an existing product is better than rolling an in-house version. The main difference being that K-9 is not independent now, the companies that do this with Blender don't end up owning Blender.
So with any acquisition there's some cause for caution, but overall I am inclined to be pretty optimistic about this. I use K-9 today, and I would like to see K-9 get more resources and to get more parity with other clients. I'm a little bit hesitant about my primary email client on my phone entering an experimental phase where its interface is going to change a lot. Again, concerns, but overall this seems like actually pretty good news.