So as far as I can find, Zero-G is difficult terrain (so half movement) and has some other penalties (like the -20 test for charging or running, failure = prone). Voidborn get a +30 for movement in Zero-G, does that mean they get a +30 to dodge? Are there any other penalties?

Edit: On Page 98, it says Acrobatics in Zero-G are at a -20 penalty

The void born gets +30 to cancel out (and surpass) the -20 movement check in zero-g.

I think that all combat actions with the "Movement" subtype in table 7-1 on page 219 falls under this category. So dodge gets the modifiers.

I.e. a void born has a total of +10 dodge in zero-g.

It seems odd that the -20 is only mentioned in acrobatics, rather than the actual section on Zero-G movement (which just goes "Difficult Terrain" and lists the other important notes)

It is actually also listed in Table 7-25 on page 246.

Thank you! It seems to look more to the modifier for the charge/run and structured time tests, than apply to dodge and the like. But it is something concrete at least.