Horrifying. Always read your contracts and remember to abide by what you have signed, or don't sign at all.
For companies, you all should be very clear on what your contract allows and doesn't allow. That will help everyone and allow folks to self select away from you if they need or want to.
I understand the motivation of Gigster (own as much of the output of a developer as possible while at the same time pushing as much risk as possible to the developer), but agree that such spooky terms don't help attract talent.
The only way to get rid of these kind of labor unfriendly terms in the current environment is to avoid them like the plague.