Have you had success replying to those posts and asking 'Would you consider a freelancer for this position?' or how do you go about it since these threads seem to implicitly indicate that they're looking for employees?
I definitely don't do that. I posted once in the who-wants-to-be-hired thread, but I don't do that anymore, because I had one guy get really angry once he realized I didn't want to be his employee, he accused me of bait-and-switching him to outsourced development (LOL). I was open to perm/ft work at the time for the right fit (which this guy wasn't), but his response was so visceral that I decided it was just a bad form to post there knowing for 95% of inquiries there was no chance of me going perm and that for the longshot 5% i would probably find them through another channel.
Don't ask, tell. Tell them your credentials and how you're going to solve their immediate problem. Don't beg them "please hire me even though I'm remote!", spell out that you're a seasoned veteran, here's my code on Github and my open source projects with the air of confidence that if "you don't hire me, someone else will."