The game was on a bundlestar giveaway, so it can't be gifted on steamgifts :(

That's because this game was given out for free. Once games were given for free they cannot be given away anymore. It also makes no sense to offer the soundtrack instead, as only people who already have the basegame will be able to enter this. Also they will expect you to gift them the soundtrack. You are going to receive a "Not received" feedback.

Also per rules this is called a "Misleading giveaway", as you are not gifting what the label says. This will result in a ban from the site and the giveaway will be deleted. Please delete it yourself to spare yourself being locked out from this site (if only temporary).
Please read the faq and guidelines of this site. Here you can look at punishments for several things that can go wrong.

As Ev said, once-free games can not be given away. I think people appreciate you giving it, but there is a reason behind not letting it to be gifted - imagine a huge giveaway, like hundreds of thousands. Some people have a lot of alt accounts with emails, so they can get hundreds of keys to resell, or to give it away. While only the first 5 copy gives "full" (15% in case of bundled) CV, later ones give 90% of the previous ones, it's still enough for people to gift games for it. People would spam the site with their free keys in order just to gain more CV, in hopes of levleling up and reaching more giveaways. So, this is the reason behind removing the game - preventing people farming CV from keys they got for free promotions.
I just thought that maybe if you are told the whole reason, you won't feel like it's an attack against you - you're pretty new here, you don't necessary know this.

Delete the GA before you are suspended and blacklisted by a lot of people.

people are telling you the truth, this giveaway is invalid and will get you introuble.
so please take it down before that happens.

as once a game is free its no longer allowed to be given on here, unless your simply dropping the key or giving it to someone.

Read the rules

You can't give that away.
Delete the giveaway, before you get in trouble.

Misleading giveaway and freebie giveaway - nice combo you did here...

1. Beta keys, guest passes, coupons, and free games should not be given away.
2. Giveaways should accurately reflect the game being given away. If the game is not available in the giveaway list, please contact support to have the game added, instead of posting the giveaway under an incorrect name.
3. Only enter to win games you do not already own, and do not enter to win DLC if you're missing the required base game.