Yes, the DIY form is still safe and secure. If you choose to embed a DIY form on a non-secure page of your website, the URL will not display https://, but the security seal will still display at the bottom to let users know that your form is secure. 

If donors are still nervous to donate through your page, you can provide them a direct link to the DIY form and the URL will display https://. Otherwise, you can re-embed the form on a secure page of your website.