Yes it is a keeper league.
This is the post from the rules page.
1 This will be a 12 team league played on YAHOO free
2. The league will be a 5X5 H2H league with standard Scoring
3. Each team will have 20 players
1 C, 1 1B, 1 2B, 1 SS, 1 3B, 3 OF, 2 UTIL, 2 SP, 1 RP, 5 P and 2 bench spots.
4. This will also be a keeper league where you get to keep 5 players each year