look at the amount of thanks they have, post count, join date.. says they been here and been making stuff, that they're established. all their uploads have to come with 2 virus scans, usually virustotal they upload with which is like every virus scan anyways. plus their uploads need manual approval from mods that it's clean, won't keylog ur stuff like someone else here was banned for, or have work done from other coders without consent or none of that. if their stuff gets approved, the "thanks" is how u can see they're getting upload approvals because people are downloading their content.
than of course forum rank obviously. If you can't tell by that or don't trust simply that, refer to the above, it's probably a safer bet.