Is this equal to your brawn rating? Meaning if you have brawn 1 you can only have one implant?

Yes. Also, Brawn enhancing Cybernetics will increase your Cybernetics cap, since they increase your Brawn rating.

There are a few exceptions to this rule.

Droids have a Cybernetics cap of 6 at character creation.

Ganks have a Cybenetics cap of their Brawn rating +3.

Any character who picks up the Cyber Tech specialization tree will get talents that increase their Cybernetics cap past the normal cap.

There's also a cybernetic implant that increases your cap by 2.

Remind me, can a character have more than 6? Say he's a gank with Brawn 4, or a droid with the Cyber Tech spec?

The Talent raises the cap, so yes.

I'm playing a Gank in our current campaign, and if I did my math correctly the potential maximum for them is 15 cybernetics, or something crazy like that.

Yes. Also, Brawn enhancing Cybernetics will increase your Cybernetics cap, since they increase your Brawn rating.

There are a few exceptions to this rule.

Droids have a Cybernetics cap of 6 at character creation.

Ganks have a Cybenetics cap of their Brawn rating +3.

Any character who picks up the Cyber Tech specialization tree will get talents that increase their Cybernetics cap past the normal cap.

I thought there was a rule that increases to Brawn from cybernetics specifically didn't increase your cybernetics cap?

Nope, says your cap is your Brawn rating. Their are exceptions to that like the implant, Ganks, the Talent.