Although David Nüscheler invited Karsten already some time ago to join the JSR-283 expert group, it took it's time to find the way through beaurocracy ... To save the fee of $2000, Karsten decided to sign up as an individual member instead of officially representing the TYPO3 Assocation - practically there will be hardly any difference of course.
So now after signing the Java Specification Agreement including Exhibit B and managing to fax it back a few times, Karsten is now listed as an official member of the JSR-283 expert group - congratulations!
PS: Karsten managed to leave a hint on TYPO3: They included a typo in his last name in the public listing.