[uturingmachine]

In the US there are few scenarios where there is an employment contract. The vast majority of employment is "at will"; an employee can quit (or be terminated) at any time for any reason, so long as it is not expressly forbidden by law (e.g. firing someone for race, sexual orientation, age, etc). In particular, at-will employees are not guilty of breach of contract for working multiple jobs - there is no contract

[ghaff]

However, there is typically a code of business conduct and other things along that line that an employee agrees to even if there isn't an explicit "contract" as there often is in Europe for example.

[lytefm]

Yeah if it's more like "you work for me; I pay you as long as the results are good but will fire you at will" it's much easier to pull this off while maintaining a clear conscience.