We registered this great domain in year-2003 making name well-aged and giving extra value. There are more than 2,000,000 results in Google on a "upx" search.
Some popular related searches are on; acronyms, download music videos, online colleges, car insurance, credit cards, cheap flights, flowers, life insurance, dentist, hotels
UPX.org is available and on-sale due to its owner retiring soon. In fact, a desire for retirement income is a reason the owner can do an interest-free monthly payment plan (and a buyer's benefit).
P.S. No worries about using the domain while paying. You will have the same use as if you paid purchase price up-front, and be able to use your own DNS immediately upon making your first payment.