Does a business owner also OWN his employees? He da MASSA and they're the slaves? Jerry Jones is playing that role. Why?

Slavery have existed under many names in many countries. In medieval countries peasants did not own the land they worked on except for a small plot of their own. Over time this became even worse with such peasants being forbidden to move away from the land they worked. By modern standards we would definitely call that slavery. Language even have a word "Serfs" to describe that kind of slaves. today that kind of slavery have been abolished,  Inventive people have replaced it with even never versions. "wage slavery" is one of them. You are free to work or not as you please, but if you chose not to you should not expect wages to let you buy food for your family. This new version largely depend on people NOT owning any land (where they could grow food for themselves). Slavery comes back, over and over and over.

Mortgage slavery is another version. If you do not obey you loose not just food, but also any property you possess.

Did you know that some 40% of early settlers in the US were 'indentured workers' people so indebted that it was cheaper for the government to buy their debt and then tell them "You go to colonize America now, or we put you in debtors prison for the rest of your life", than it was to find people willing to go voluntarily. The pilgrims fled from oppressive religion, many others fled from that sort of debt-slavery.

Early US bankruptsy legislation was an attempt to stop that sort of thing, but have since been considerably 'eroded' and also used by 'smart' people to make more money.

I wonder how the newest 'Mobile generation' will be enslaved. But I am sure greed will find a way.

I'm not familiar with any "Jerry Jones" thing ... but yes, sorta, employers do "own" their employees.  At least in two respects:

1 - During working hours, and
2 - During off hours the employer may hold the employee responsible for a "code of conduct" and social media postings.

i dont think so or at least he shouldnt be

It is called being the Boss. No one is owned, the players are free to go to another team or no one is being forced to play. And they are being PAID to play. Slavery don't work that way. They are under contracts though. 

This is working out the best way possible in terms of how labor contract disagreements are adjudicated..  The players union thinks that Jones (or any owner) can't do this, so they filed a grievance.  If they cannot reach a settlement between Jones and themselves, they can avail themselves of binding arbitration. 

Then since the viability of the football "business" under whatever agreement is reached can also be voted on by the ultimate deciders---those of us to whom the players and owners want to sell their product.

I think that small bump  Kaepernick  knelt on was the equivalent of "Pork Chop Hill" in the Korean war.  That is not a hill I would have chosen to die on.

Dallas Cowboys owner, Jerry Jones’s threat to punish players who kneel in protest during the national anthem violates the National Labor Act. Local 100 of the United Labor Union filed a complaint with the National Labor Relations Board in Ft. Worth, Texas. Jones is the first NFL owner to explicitly threaten discipline for the practice.
   The union says employers are banned from threatening workers for “concerted” activity. The union’s chief, Wade Rothko said Jones is bullying his employees to “unilaterlly establish a previously nonexistent condition”. 
   The law says you have the ability to act with your co-workers. And you cannot bully workers on the job.