Yes, you can use our icons for a logo, but please, note that it's officially prohibited to go to a patent office and officially patent that logo with our icons in it.
You can keep using it commercially, etc., but actually patenting it is prohibited by our License:

If you are a free account user, you will need to set a link to our website everywhere the logo is used.
If you want to edit it, please purchase our license. Also, paid usage doesn't require linking us

If you are not planning to patent the logo, you are fine and you can use the logo after your subscription expires, as all the icons you download while having the subscription are yours for a lifetime.
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