This is an issue that comes up frequently around graduation time. It is related to wanting a foreign national to come to the U.S. to give a speech, and whether or not they are required to have a visa. As with most things, there is a simple answer, and a complicated answer. The simple answer is that if the speaker does not receive any payment for an honorarium or reimbursed travel expenses for their trip, they will not need a visa, and can travel into the U.S. via either a B1 business visa, or the visa waiver program (VWP). Performing artists have slightly different rules. An artist who is currently a professional in his/her home country needs to obtain a special visa to be able to perform in the United States, even if they are not going to be paid for their services. There are a few exceptions to these rules, such as a speaker being eligible to enter the U.S. without a visa even if they are receiving payment for an honorarium or reimbursed travel expenses if:
They are appearing for no more than 9 days at any one organization/institution,
They are being paid by an organization/institution that fits categories listed in INA 212(p),
The honorarium is strictly for services rendered for the institution, and
The speaker has spoken at fewer than 5 institutions in the past 6 months
Each and every one of those requirements must be met, or the speaker will need to obtain an O visa, and be able to prove that they are prominent in their field, either nationally or internationally. As an O visa can take months to obtain, it is a good idea to apply roughly a year before the scheduled speech.