StrawPay hasn't published any details of their work publicly; if they
wanted credit on the mailing list they should have done that.

There's a brief discussion here:

https://www.reddit.com/r/Bitcoin/comments/2r3ri7/strawpay_cheap_and_secure_micropayments/

But yes, they are developing it before publishing more details that may be subject to change post-implementation experience anyway.

I'm genuinely looking forward to a concrete fork proposal. Any ETA on
when the blocksize increase code will go in Bitcoin XT?

Great! I am waiting for Gavin to finish writing the patches. Once he has a patch and there's been some time for review, I guess it will go in, assuming no other issues.