Its probably a little early yet for the usual non runner no bet offers on the Grand National. The idea of non runner free bet is something that Betvictor have tried with Cheltenham and clearly feel it is worth repeating on the Grand National.
If you are considering an ante post bet on the National at this time, this is a better option than taking a standard ante post bet, which will lose if your horse does not run. However there are a couple of things to be aware of.
Firstly the free bet will be returned as promo cash which must be used on the day it is refunded. This is very different from non runner money back. Promo cash is stake not returned, so if your free bet wins you don't get the stake of your original bet back. Although it doesn't say so in the T&Cs of this offer, Betvictor promo cash usually has a 4x bonus wagering requirement.
Secondly, Betvictor are quite good at closing accounts and will refund the balance in your account back to your card if they do this. This will not include any promo cash balance that you have in your account, which will be lost. So if your account is closed between your ante post bet and Grand National day, you will get your winnings if your bet wins, but you won't get the free bet if your horse does not run.