I was able to download Ema's version of the 4E character sheets for free. Ema's asked for for money for the ability to store your character data on her site and to pay for its upkeep. The product itself (character sheets) was available for free.
EN World has a Wiki and other services that provide information on WotC's IP, some taken straight from the PHB, others being interpretations made by fans like Ema. EN offer's that information for free but request that you contribute to the upkeep of the site by becoming a community suporter. Both sites request money (optional) to help in the payment of the site.
For the sake of argument, let's just imagine that ENworld had anywhere near the same amount of things who aren't comme il faut as Ema's site had.
The difference is still the following. At ENworld you can get everything you want, for free (except the search function! but that's hardly related to WotC's IP or whatnot). At Ema's you could get some things for free, but if you wanted everything, you had to pay.
Analogy:
Two guys make their own adventures, set in forgotten realms. They use monsters, items and traps straight out of the three core books. They both distribute these via their website.
WotC doesn't care. It's fan-stuff, and WotC likes their fans, because lets face it, they wouldn't exist without.
Then something changes. One site says: hey, if you guys want to be able to search all our adventures for key-words, you have to pony up some cash.
WotC still doesn't care. The site makes money off a search function, it's not their business.
Then the other guy says: Hey, from now on, you can still get some of my adventures for free, but the new stuff, you have to pay for it.
Suddenly WotC cares. Because the second guy is now in fact selling and making money directly of WotC's IP.
Okay, someone could probably come up with a much better analogy, but the point was just to show that there is a huge difference between what ENworld is and what Ema's site was.