The NFL is back in business — belatedly and who knows for how long.

The league Thursday finally got around to complying with a federal judge’s order to lift the lockout, announcing that all team facilities will reopen Friday morning at 8 a.m. while saying free agency and the trading of players will resume, potentially as soon as Monday.

But the announcement by the owners came grudgingly and not without more risk on their part of incurring the wrath of U.S. District Judge Susan Nelson after she twice ruled in favor of the players in their antitrust battle against the league.

NFL’S NOTICE TO TEAMS

The owners unsuccessfully sought a freeze from Nelson of her injunction Monday lifting the lockout, and are now going over her head and seeking the same thing from the 8th Circuit Court of Appeals.

That decision from the appeals court could come as soon as Thursday or Friday (although Monday is more likely), and the lockout would be reinstated immediately if the court sides with the owners and stays the injunction.

“Pending further guidance from the Eighth Circuit, we believe it is appropriate for clubs to take additional steps in response to the preliminary injunction,” the league said in its statement.

Legal experts tell The Post there is far from any guarantee the league will get that stay from the appeals court. The NFL also appealed Nelson’s ruling to the Eighth Circuit court, but that ruling is weeks from being decided.

Individual clubs remained in a state of confusion after the NFL’s announcement, unsure of specifically when free agency or the trading of players would start and how it might impact the NFL Draft that starts Thursday.

Despite Nelson’s insistence that the lockout be lifted immediately, the league claimed free agency and trading players is too complicated to restart immediately.

As a result, teams as of right now can only trade picks and no players during the three-day draft that starts tonight at Radio City Music Hall.

Everything else is back to business as usual: offseason workouts, medical treatment, drug rehab, organized team activities (OTAs), and minicamps. Teams also are allowed to interact with their players and distribute playbooks.