I think it only means if you do get paid reasonable amounts for open source work, you don't have to pay tax on that.
So between jobs it shouldn't matter since you wouldn't pay taxes anyway, unless you worked a lot and received a lot of donations. But if you contribute after hours of a regular job, this would ensure you still get the full amount the foss project receives.

There is also mention of assistance with administration, which I'm not sure what that entails.