With no Collective Bargaining Agreement in place between the NFL owners and players, team will not be allowed to sign the players once they draft them in the NFL Draft later this month In addition, once the seven round draft is complete, there is usually a flurry of activity as teams try to round out their rosters by contacting and signing undrafted free agents.
The Baltimore Ravens have had great success after the draft finding excellent players that were left undrafted (Bart Scott, Jameel McClain) and would hope to be able to find the next great diamond-in-the-rough in this year's group. However, there cannot be any undrafted free agents contacted or signed without a new CBA signed and in place, which just is not going to happen prior to the end of this month.
Therefore, these players will remain in NFL limbo, but that will not stop the UFL from trying to "poach" those players for their season. The UFL pays a lot less than the NFL does for undrafted free agents, even less than these guys would get if they spent the entire season on an NFL team's practice squad. However, who knows what will happen with the labor issue in the NFL and the UFL might be less but it is also a more "sure thing" than the NFL right now.
See more on this dilemma facing those UFA's at USAToday.com.