Just wondering.. I have a bunch that I would like to share, for free.. But, didn't want the game police getting involved.. lol
If they're older generation console titles then there's little to worry about it. It's new gen consoles that are (obviously) a concern - the site doesn't allow protos from current gen consoles either. Legally, just like 99.9% of any proto dumps, it's always illegal because you don't own the rights to the game or have permission to share it. There's no grey area - it's just plain illegal. The question is: who would you be affecting? (this is the question you have to ask yourself) If it's a SNES proto (for example) then it's a safe bet Nintendo don't care - it doesn't take Sherlock Holmes to reach that conclusion. It's also highly unlikely the actual dev team would care either, seeing as all involved would have moved on to pastures new a long, long, long, time ago. I'm certainly curious to know what protos you have? (if you don't mind me asking!)
As anroldlayne said, it's always illegal in itself as it's basically piracy. But for older systems the chances of you getting sued are almost non-existent. My advice would be to use judgment as to what you release so that it doesn't monetarily harm anyone and that you don't make money out of it, and release as anonymously as possible. That's what most members I know here do.
Contact/PM one of the staff here. They can probably take a look on a case by case basis. I'm excited to see what's in your possession that may not have been exposed yet.