Yes. You will get 3 months of subscription free if you already own a Relab product.
Note that you can only get free months credited by signing up for a monthly subscription, NOT a yearly subscription. When you sign up for a new Gobbler account, you'll be prompted to enter your iLok username – make sure this account is the same account that your Relab Development perpetual/permanent licenses are in. If you already have a Gobbler account, make sure your iLok account is linked to your Gobbler account. Gobbler will automatically credit you with your free months when you sign up for a monthly subscription.