If a founder is contributing IP to an LLC and receives a captital account equal to the value of the IP, is the founder liable for taxes on the amount in the capital account?
(Assuming you're in the US, because you didn't mention jurisdiction)
No, if the "check-the-box" election is to treat the LLC as a disregarded entity. It becomes the basis of the contributor in the partnership. If elected to treat the LLC as a corporation, tax consequences may be more complicated.
Talk to a local tax adviser.