Smok built a free TCPIP to serial converter PCB. Give your projects an internet connection by simply connecting to this board over a serial interface.
If you build a free PCB we’ll send you another one! Blog about it, post a picture on Flicker, whatever – we’ll send you a coupon code for the free PCB drawer.
Check this out..its a similar product..in a smaller form factor..
http://entesla.com/converters/serial-ethernet-converter
Check this one out also.
http://www.wiznet.co.kr/Sub_Modules/en/product/Product_Detail.asp?cate1=&cate2=&cate3=&pid=1040
Model WIZ110SR flash upgradable
This one can be had for about $25 usd from Saelig and has a registered MAC address. I have used several in projects and it has not given me any trouble.
Yeah, the market is pretty saturated and that’s why we never really continued this project. As far as I know though, there are no similar adapters that are open hardware.