I'm afraid you can't. Even if you buy Explaindio Elements Free Footage Module without the Standard Version, you will not be able to use Explaindio Elements without the Standard version.
Here is why:
1. Explaindio Elements Standard Version is the main product which comes as Monthly, Annual or a Special One-Off payment subscription.
2. Explaindio Elements Free Footage Module is an Upgrade or Up-sell which gives you ability to get Royalty Free Footage.
3. Since Explaindio Elements Free Footage Module is not independent, you will need to subscribe for the main product Explaindio Elements Monthly, Annual or an Special One-Off payment subscription. Else you can't use Explaindio Elements with only Explaindio Elements Free Footage Module in your account.