You do not need OOTP 6.5 in order to join, as the website for the league is set up to where you submit your lineups in a similar fashion to as if you had the game. But if you do have 6.5, there's exporting too.
This is the main site: Vis-à-Vis Baseball League
This is the OOTP site: V-a-V :: OOTP 6 Generated Website
And the forums for it: Home | Vis-à-Vis Baseball League
Ultimately, you're able to do just about everything on the website. Make a trade block, negotiation contracts, set your minors, set your major league roster, offer trades to teams, etc. The league has 40 man rosters, waivers, August waiver trading, compensation based on a formula (so you can lose picks, basically real life-ish) which you're able to track on the main site, and the main site also calculates a sabermetrician's favorite stat...WAR. You can trade picks (all rounds including sandwich picks from comp).
Simming is 3 times a week, usually about 6 games a pop. Drafts have been a mix of players from the past. The wealth of talent is less than MSL, and for those that fondly remember, it's more comparable to missionhockey's former league, S3SL. The draft is also a lot different, as it starts middle of the season and goes throughout the rest of the season. Players start in your minors the following season (we draft through the main site, there are actual time limits and auto picks..but you can set draft lists too).
Right now, the Oakland A's and the Baltimore Orioles definitely need owners, and possibly the New York Yankees.
If interested, you'll need to sign up the forums, the third link. Doesn't matter what you make your username, it'll ultimately be changed to reflect the team you run. If you want in, please let me know so that I can let the commissioner know to give you full access to everything. I've known him since high school and in fact, he lives just a county away. He's been doing this forever, basically.
Any questions, let me know!