Only if the app provides 1. prominently-displayed, informed consent, 2. an option to opt-out without losing app functionality, or 3. joining the botnet provides some kind of actual benefit to the user, besides just money to the developer.
There is really not good excuse to bundle this functionality with an unrelated app in the first place.
Apparently at least one of the apps mentioned does that. From the article
>A Pac-Man smart TV app from Bright Data offers users the choice between viewing ads in the game or agreeing to allow their TV to serve as a residential proxy node.
Some residential proxy providers offer a few cents for the use of your network.
No need of (2) and (3) - the user can choose to not install/use the app. (1) is the right fair boundary.
Add to that list respecting the TOS of the user's ISP so that the user does not get banned, and providing some sort of remuneration if illicit activity through the proxy causes problems for the primary user, and then _maybe_ you could call this all not shady as fuck.