My guess would be the US Govt would argue that it is not "benefitting" from the cooperation:
"Involuntary servitude or Involuntary slavery is a United States legal and constitutional term for a person laboring against that person's will to benefit another, under some form of coercion other than the worker's financial needs." [1]
Or..that Apple is not a person. Or..that Apple is not being coerced.
Who knows :/
1. Wikipedia: https://en.wikipedia.org/wiki/Involuntary_servitude
I like the way that financial needs is considered coercion, but is just exempted. I wonder what the basis for the exemption is. How can it be justified compared to other forms of coercion (or the use of financial coercion in other areas) without resorting to special pleading?
Specific performance of personal services is something courts are skittish about compelling but there are uncountable nuances. In particular I don't believe that the 13th has ever been held to apply to non-natural persons (eg corporations or trusts).
While some of these statutes—such as Florida’s sanctions for impudence—went beyond the mere punishing of breach of contract, all of them operated within a thick web of other laws that had the effect of suppressing competition between employers, further restricting the choices available to African-American workers. First, states passed anti-enticement laws that created penalties for those who tried to lure away employees with offers of better wages or working conditions. Second, emigrant agents, who recruited African-American workers in areas of low employment and transported them to jobs in distant, labor-starved markets, were subject to onerous licensing and taxation requirements.355 Georgia, for example, levied a tax of $500 on emigrant agents for each county in which they operated.356 Mississippi made it a crime to “entice . . . [any] negro” to leave the state.
Courts apply the Thirteenth Amendment to cases involving the "badges and incidents of slavery." Usually, that refers to some form of systematic oppression of African Americans. It definitely doesn't include forcing Apple to write and sign code.The trouble is, if Apple doesn't raise it early on, it won't be considered, and we'll never really know.