There are two quite different interpretations of this quote: it either says something about scientists, or something about scientific truths, and I'm not sure which is the intention.
The two messages I see are:
Scientists just enjoy seeking truths, you don't need to give them the incentive of practical applications in order for them to do science, so any truths that can be discovered will be, regardless of their usefulness.
There are an awful lot of true things. The ones that we know might not be the most useful, but they are the ones that happen to lie in the (extremely small?) subset of true things that humans are capable of understanding.
To an extent, I guess both of these are true... which one was Oppenheimer aiming at?
[one interpretation of Oppenheimer:] There are an awful lot of true things. The ones that we know might not be the most useful, but they are the ones that happen to lie in the (extremely small?) subset of true things that humans are capable of understanding.
Quibble: Two things you might have missed:
A monthly thread for posting rationality-related quotes you've seen recently (or had stored in your quotesfile for ages).