The lottery part is irrelevant, how interest is allocated to holders makes exactly zero difference to what a bond is.
Or perhaps you don't understand what "fund SETI" means?. Where is this money to invest coming from (the money from the bonds is going to fund SETI after all so it can't be it)? And why don't they just use that to fund SETI instead of adding the pointless bonds middle man?
A bond is simply a loan. The bond issuer gets a bunch of money up front and then has to pay it back in the future. That is fine for things like a bank that will take the money raised and loan it to others thus generating the required additional funds. That's fine for things like the government wanting to fund a project (or a war, or day to day operations) they will collect taxes in the future to pay back the funds and interest. That's fine for things like a company wanting to fund an expansion of some sort, they'll have the future revenues from the expansion to pay back the debt. Heck if you want to buy a house by issuing bonds instead of going with a traditional mortgage have at it - the theory being your future income will allow you to pay the interest and principal and if not then the house can be sold to hopefully get back most of it.
But what revenue stream does SETI have in order to pay back these bonds? And do they really need the expense of the bond management and interest payments to access that future revenue early (via borrowing with bonds)?