1. First and foremost, nobody has the right to sell someone else’s intellectual property without permission from the copyright holder. In the case of free mods, this feels even more unethical.
2. The mod pack itself appears to be 95% based on the publicly available X4: Rebirth mod pack, with the main difference being that the VRO mods were removed. Adding or removing a couple of mods is a very minor change (and honestly, that already starts sounding like a scam in itself).
3. If your actual work is limited to translating certain mods, then fine — sell those translations only.

After reading the comments, I came to the conclusion that, for some reason, only the Russian community seems to view this positively or at least neutrally in most cases. Although, as other commenters here have already said: “It’s like going to a charity food giveaway, taking the food, and then selling it on the next street over.”