Hey! There's some great replies here already, I thought I'd add just what my thoughts were when originally setting up this jam.
One of the big influences for PROCJAM was Sophie Houlden's Fishing Jam, way back when. The jam let you pick 7 days out of a month to work on a game, so it was time limited but flexible. I did my best ever jam work in that jam, because I picked weekend days and took my time to think in between.
When starting PROCJAM, one of the goals was to bring people from across generative software to make stuff in the same space, so people could see how other folks worked, what ideas and techniques they used, and get sharing and inspiring each other. The problem is, traditional game jams kind of exclude a lot of that. Fast crunching stops lots of people entering if they have jobs or kids or other stuff. And picking winners means people feel pressured to be the best, or discouraged from making messes and experimenting. PROCJAM is definitely a bit different from the big game jams. But actually, a lot of jams work like this now! It's increasingly popular.
Lots of people - myself included - will only work on something during the time limit this year. So you can definitely join in and do PROCJAM like that, it's kind of the standard way for many people. All we do is make sure you have the option to do something else if you need it.
I hope you take part in PROCJAM and enjoy it, either way :)