Wenner-Gren grants and fellowships are not subject to US taxes if you are: 1) not normally subject to US taxes by nature of your citizenship or tax residency status and 2) 100% of the research or conference/workshop activities funded by Wenner-Gren is conducted outside the US. However, there may be tax implications in your country of citizenship or tax residence, and you should seek advice from an appropriate tax advisor.
Occasionally, an applicant may have a Conference application and another program application pending at the same time. You cannot apply for two grants at the same time (such as a Hunt Fellowship and a Post-Ph.D. grant), nor have two formal applications pending at the same time. Normally, you must have completed any previous grant awarded to you by the Foundation before submitting a new application.