It is possible to read MOBI lending library ebooks on the EZ Reader, but you have to manually set the clock to get it to work. See
Library eBooks Readable = Win.
It is a shame that Amazon threw its weight around at MobileRead, because kindlefix does not circumvent DRM and is entirely legal in the US. It is still available from its original blog posting (another indication of its legality).
It can be difficult to learn the "command line", but the good news is that the
Kindle Visual Guide, once decimated by Amazon's strong arm tactics, again has sections on Command Prompt Vista/XP/Mac and Install Python Windows. This might be enough (with the readme.txt that comes with kindlefix) to get you to the point where lending library MOBIs work on your Kindle.
If not, see if you can use
KindleDRM. This python script does not touch DRM, be it will tell you if an AZW/MOBI/PRC ebook has DRM or not. Even Amazon would likely agree that this script is legal, so we can tell you how to get it working (and all python ebook scripts are similar). If you can use kindledrm, you can use kindlefix and the kindle python script that can't be named.