It was a risk, yeah, but he was pretty professional about the whole deal, which made me trust him more. He showed me the other translation projects, including Ao Oni, he's done, was very responsive to my replies and requests, and promised to give me the translated build beforehand so I could run through it myself and double check his work. Google Translate doesn't do a good localization justice, but at least it helped me realize that, if nothing else, he was pretty serious about the endeavor.
Most importantly: his English was spot on. I've gotten a couple of requests to translate some of my other games where their English was so broken they could have been asking me for something totally random, like a cooking recipe.
If it were Soul Sunder, Remnants of Isolation, or other projects that were comparatively closer to me, then I would have said no. With Psychostasis, I felt it was more worth the risk, and it turned out to pay off well.