First, kudos to ECMA for coming out with a test suite - having a benchmark for compatibility will drive the browser vendors to improve their interoperability. Everyone wins there. Also, the visual design of the page is very nice - something we don't always get from standards bodies.
Second, kudos to the IE team for getting the top score with their IE 10 preview! And IE 9 is way up there also. Seriously, good job guys. We know that I have my problems with Microsoft's browser policies, but nobody can deny that the IE team is doing great work over there.
Now, the bad news (emphasis mine):
Test262 is being developed by the members of Ecma TC39. Ecma's intellectual property policies, permit only Ecma members to directly contribute code to the project. However, a public mailing list is used to coordinate development of Test262. If you wish to participate in the discussion please subscribe. Bug reports and suggestions should be sent to the mailing list.
If those are your policies, guys, change your policies. This is exactly the kind of thing that should be open source. You're not trying to sell it. Lots of talented people have incentive to contribute to it.