Niner Tim Ryan, broadcaster commented later that 1 year = quit, 5 years = retire.
Borland received a 617,000 signing bonus. I would imagine since it was a 4 year deal, he'd just give back the prorated amount, there have been owners taking players to court over these issues. So there is some precedent. There have been issues with the IRS, in terms of cash basis tax, where the player had already paid the tax on the bonus, the team would then just get the portion minus the tax.